Move Extensiblity into API/wix

102 files changed, 4509 insertions, 0 deletions

diff --git a/src/api/wix/CSharp.Build.props b/src/api/wix/CSharp.Build.props
new file mode 100644
index 00000000..81d24ad1
--- /dev/null
+++ b/src/api/wix/CSharp.Build.props
@@ -0,0 +1,13 @@
+<!-- Copyright (c) .NET Foundation and contributors. All rights reserved. Licensed under the Microsoft Reciprocal License. See LICENSE.TXT file in the project root for full license information. -->
+<!--
+  Do NOT modify this file. Update the canonical version in Home\repo-template\src\CSharp.Build.props
+  then update all of the repos.
+-->
+<Project>
+  <PropertyGroup>
+    <CheckForOverflowUnderflow>true</CheckForOverflowUnderflow>
+    <SignAssembly>true</SignAssembly>
+    <AssemblyOriginatorKeyFile>$([System.IO.Path]::GetFullPath($(MSBuildThisFileDirectory)wix.snk))</AssemblyOriginatorKeyFile>
+    <NBGV_EmitThisAssemblyClass>false</NBGV_EmitThisAssemblyClass>
+  </PropertyGroup>
+</Project>
diff --git a/src/api/wix/Custom.Build.props b/src/api/wix/Custom.Build.props
new file mode 100644
index 00000000..889fb62e
--- /dev/null
+++ b/src/api/wix/Custom.Build.props
@@ -0,0 +1,6 @@
+<!-- Copyright (c) .NET Foundation and contributors. All rights reserved. Licensed under the Microsoft Reciprocal License. See LICENSE.TXT file in the project root for full license information. -->
+<Project>
+  <PropertyGroup Condition="'$(Configuration)'=='Release'">
+    <TreatWarningsAsErrors>true</TreatWarningsAsErrors>
+  </PropertyGroup>
+</Project>
diff --git a/src/api/wix/Directory.Build.props b/src/api/wix/Directory.Build.props
new file mode 100644
index 00000000..f83cc154
--- /dev/null
+++ b/src/api/wix/Directory.Build.props
@@ -0,0 +1,29 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!-- Copyright (c) .NET Foundation and contributors. All rights reserved. Licensed under the Microsoft Reciprocal License. See LICENSE.TXT file in the project root for full license information. -->
+<!--
+  Do NOT modify this file. Update the canonical version in Home\repo-template\src\Directory.Build.props
+  then update all of the repos.
+-->
+<Project>
+  <PropertyGroup>
+    <Configuration Condition=" '$(Configuration)' == '' ">Debug</Configuration>
+    <EnableSourceLink Condition=" '$(NCrunch)' == '1' ">false</EnableSourceLink>
+    <MSBuildWarningsAsMessages>MSB3246</MSBuildWarningsAsMessages>
+
+    <ProjectName Condition=" '$(ProjectName)' == '' ">$(MSBuildProjectName)</ProjectName>
+    <BaseOutputPath>$([System.IO.Path]::GetFullPath($(MSBuildThisFileDirectory)..\build\))</BaseOutputPath>
+    <BaseIntermediateOutputPath>$(BaseOutputPath)obj\$(ProjectName)\</BaseIntermediateOutputPath>
+    <OutputPath>$(BaseOutputPath)$(Configuration)\</OutputPath>
+
+    <Authors>WiX Toolset Team</Authors>
+    <Company>WiX Toolset</Company>
+    <Copyright>Copyright (c) .NET Foundation and contributors. All rights reserved.</Copyright>
+    <PackageLicenseExpression>MS-RL</PackageLicenseExpression>
+    <Product>WiX Toolset</Product>
+  </PropertyGroup>
+
+  <Import Project="CSharp.Build.props" Condition=" '$(MSBuildProjectExtension)'=='.csproj' and Exists('CSharp.Build.props') " />
+  <Import Project="Cpp.Build.props" Condition=" Exists('Cpp.Build.props') And '$(MSBuildProjectExtension)'=='.vcxproj' " />
+  <Import Project="Wix.Build.props" Condition=" Exists('Wix.Build.props') And '$(MSBuildProjectExtension)'=='.wixproj' " />
+  <Import Project="Custom.Build.props" Condition=" Exists('Custom.Build.props') " />
+</Project>
diff --git a/src/api/wix/Directory.Build.targets b/src/api/wix/Directory.Build.targets
new file mode 100644
index 00000000..cb988931
--- /dev/null
+++ b/src/api/wix/Directory.Build.targets
@@ -0,0 +1,56 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!-- Copyright (c) .NET Foundation and contributors. All rights reserved. Licensed under the Microsoft Reciprocal License. See LICENSE.TXT file in the project root for full license information. -->
+<!--
+  Do NOT modify this file. Update the canonical version in Home\repo-template\src\Directory.Build.targets
+  then update all of the repos.
+-->
+<!--
+  Replace PackageReferences with ProjectReferences when the projects can be found in .sln.
+  See the original here: https://github.com/dotnet/sdk/issues/1151#issuecomment-385133284
+-->
+<Project>
+  <PropertyGroup>
+    <CreateDocumentation Condition=" '$(CreateDocumentationFile)'!='true' ">false</CreateDocumentation>
+    <DocumentationFile Condition=" '$(CreateDocumentationFile)'=='true' ">$(OutputPath)\$(AssemblyName).xml</DocumentationFile>
+  </PropertyGroup>
+
+  <PropertyGroup>
+    <ReplacePackageReferences>true</ReplacePackageReferences>
+    <TheSolutionPath Condition=" '$(NCrunch)'=='' ">$(SolutionPath)</TheSolutionPath>
+    <TheSolutionPath Condition=" '$(NCrunch)'=='1' ">$(NCrunchOriginalSolutionPath)</TheSolutionPath>
+  </PropertyGroup>
+
+  <Choose>
+    <When Condition="$(ReplacePackageReferences) AND '$(TheSolutionPath)' != '' AND '$(TheSolutionPath)' != '*undefined*' AND Exists('$(TheSolutionPath)')">
+
+      <PropertyGroup>
+        <SolutionFileContent>$([System.IO.File]::ReadAllText($(TheSolutionPath)))</SolutionFileContent>
+        <SmartSolutionDir>$([System.IO.Path]::GetDirectoryName( $(TheSolutionPath) ))</SmartSolutionDir>
+        <RegexPattern>(?&lt;="[PackageName]", ")(.*)(?=", ")</RegexPattern>
+      </PropertyGroup>
+
+      <ItemGroup>
+        <!-- Keep the identity of the PackageReference -->
+        <SmartPackageReference Include="@(PackageReference)">
+          <PackageName>%(Identity)</PackageName>
+          <InSolution>$(SolutionFileContent.Contains('\%(Identity).csproj'))</InSolution>
+        </SmartPackageReference>
+
+        <!-- Filter them by mapping them to another ItemGroup using the WithMetadataValue item function -->
+        <PackageInSolution Include="@(SmartPackageReference->WithMetadataValue('InSolution', True))">
+          <Pattern>$(RegexPattern.Replace('[PackageName]','%(PackageName)') )</Pattern>
+          <SmartPath>$([System.Text.RegularExpressions.Regex]::Match('$(SolutionFileContent)', '%(Pattern)'))</SmartPath>
+        </PackageInSolution>
+
+        <ProjectReference  Include="@(PackageInSolution->'$(SmartSolutionDir)\%(SmartPath)' )"/>
+
+        <!-- Remove the package references that are now referenced as projects -->
+        <PackageReference Remove="@(PackageInSolution->'%(PackageName)' )"/>
+      </ItemGroup>
+
+    </When>
+  </Choose>
+
+  <Import Project="Wix.Build.targets" Condition=" Exists('Wix.Build.targets') And '$(MSBuildProjectExtension)'=='.wixproj' " />
+  <Import Project="Custom.Build.targets" Condition=" Exists('Custom.Build.targets') " />
+</Project>
diff --git a/src/api/wix/README-Extensibility.md b/src/api/wix/README-Extensibility.md
new file mode 100644
index 00000000..003acd4d
--- /dev/null
+++ b/src/api/wix/README-Extensibility.md
@@ -0,0 +1,2 @@
+# Extensibility
+WixToolset.Extensibility - interfaces to extend the WiX Toolset
diff --git a/src/api/wix/WixToolset.Extensibility.sln b/src/api/wix/WixToolset.Extensibility.sln
new file mode 100644
index 00000000..94ce905c
--- /dev/null
+++ b/src/api/wix/WixToolset.Extensibility.sln
@@ -0,0 +1,36 @@
+Microsoft Visual Studio Solution File, Format Version 12.00
+# Visual Studio 15
+VisualStudioVersion = 15.0.26730.8
+MinimumVisualStudioVersion = 15.0.26124.0
+Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "WixToolset.Extensibility", "src\WixToolset.Extensibility\WixToolset.Extensibility.csproj", "{AA049009-D7D9-4C63-8E0D-83206ADCFBD1}"
+EndProject
+Global
+        GlobalSection(SolutionConfigurationPlatforms) = preSolution
+                Debug|Any CPU = Debug|Any CPU
+                Debug|x64 = Debug|x64
+                Debug|x86 = Debug|x86
+                Release|Any CPU = Release|Any CPU
+                Release|x64 = Release|x64
+                Release|x86 = Release|x86
+        EndGlobalSection
+        GlobalSection(ProjectConfigurationPlatforms) = postSolution
+                {AA049009-D7D9-4C63-8E0D-83206ADCFBD1}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+                {AA049009-D7D9-4C63-8E0D-83206ADCFBD1}.Debug|Any CPU.Build.0 = Debug|Any CPU
+                {AA049009-D7D9-4C63-8E0D-83206ADCFBD1}.Debug|x64.ActiveCfg = Debug|Any CPU
+                {AA049009-D7D9-4C63-8E0D-83206ADCFBD1}.Debug|x64.Build.0 = Debug|Any CPU
+                {AA049009-D7D9-4C63-8E0D-83206ADCFBD1}.Debug|x86.ActiveCfg = Debug|Any CPU
+                {AA049009-D7D9-4C63-8E0D-83206ADCFBD1}.Debug|x86.Build.0 = Debug|Any CPU
+                {AA049009-D7D9-4C63-8E0D-83206ADCFBD1}.Release|Any CPU.ActiveCfg = Release|Any CPU
+                {AA049009-D7D9-4C63-8E0D-83206ADCFBD1}.Release|Any CPU.Build.0 = Release|Any CPU
+                {AA049009-D7D9-4C63-8E0D-83206ADCFBD1}.Release|x64.ActiveCfg = Release|Any CPU
+                {AA049009-D7D9-4C63-8E0D-83206ADCFBD1}.Release|x64.Build.0 = Release|Any CPU
+                {AA049009-D7D9-4C63-8E0D-83206ADCFBD1}.Release|x86.ActiveCfg = Release|Any CPU
+                {AA049009-D7D9-4C63-8E0D-83206ADCFBD1}.Release|x86.Build.0 = Release|Any CPU
+        EndGlobalSection
+        GlobalSection(SolutionProperties) = preSolution
+                HideSolutionNode = FALSE
+        EndGlobalSection
+        GlobalSection(ExtensibilityGlobals) = postSolution
+                SolutionGuid = {BB8820D5-723D-426D-B4A0-4D221603C5FA}
+        EndGlobalSection
+EndGlobal
diff --git a/src/api/wix/WixToolset.Extensibility/AssemblyInfo.cs b/src/api/wix/WixToolset.Extensibility/AssemblyInfo.cs
new file mode 100644
index 00000000..b3740b2a
--- /dev/null
+++ b/src/api/wix/WixToolset.Extensibility/AssemblyInfo.cs
@@ -0,0 +1,9 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved. Licensed under the Microsoft Reciprocal License. See LICENSE.TXT file in the project root for full license information.
+
+using System;
+using System.Reflection;
+using System.Runtime.InteropServices;
+
+[assembly: AssemblyCulture("")]
+[assembly: CLSCompliant(true)]
+[assembly: ComVisible(false)]
diff --git a/src/api/wix/WixToolset.Extensibility/BaseBinderExtension.cs b/src/api/wix/WixToolset.Extensibility/BaseBinderExtension.cs
new file mode 100644
index 00000000..3869d1ed
--- /dev/null
+++ b/src/api/wix/WixToolset.Extensibility/BaseBinderExtension.cs
@@ -0,0 +1,47 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved. Licensed under the Microsoft Reciprocal License. See LICENSE.TXT file in the project root for full license information.
+
+namespace WixToolset.Extensibility
+{
+    using WixToolset.Extensibility.Data;
+    using WixToolset.Extensibility.Services;
+
+    /// <summary>
+    /// Base class for creating a resolver extension.
+    /// </summary>
+    public abstract class BaseBinderExtension : IBinderExtension
+    {
+        /// <summary>
+        /// Context for use by the extension.
+        /// </summary>
+        protected IBindContext Context { get; private set; }
+
+        /// <summary>
+        /// Messaging for use by the extension.
+        /// </summary>
+        protected IMessaging Messaging { get; private set; }
+
+        /// <summary>
+        /// BackendHelper for use by the extension.
+        /// </summary>
+        protected IBackendHelper BackendHelper { get; private set; }
+
+        /// <summary>
+        /// Called at the beginning of bind.
+        /// </summary>
+        public virtual void PreBind(IBindContext context)
+        {
+            this.Context = context;
+
+            this.Messaging = context.ServiceProvider.GetService<IMessaging>();
+
+            this.BackendHelper = context.ServiceProvider.GetService<IBackendHelper>();
+        }
+
+        /// <summary>
+        /// Called at the end of bind.
+        /// </summary>
+        public virtual void PostBind(IBindResult result)
+        {
+        }
+    }
+}
diff --git a/src/api/wix/WixToolset.Extensibility/BaseBurnBackendBinderExtension.cs b/src/api/wix/WixToolset.Extensibility/BaseBurnBackendBinderExtension.cs
new file mode 100644
index 00000000..da570af0
--- /dev/null
+++ b/src/api/wix/WixToolset.Extensibility/BaseBurnBackendBinderExtension.cs
@@ -0,0 +1,94 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved. Licensed under the Microsoft Reciprocal License. See LICENSE.TXT file in the project root for full license information.
+
+namespace WixToolset.Extensibility
+{
+    using System;
+    using System.Collections.Generic;
+    using System.Linq;
+    using WixToolset.Data;
+    using WixToolset.Data.Burn;
+    using WixToolset.Extensibility.Data;
+    using WixToolset.Extensibility.Services;
+
+    /// <summary>
+    /// Base class for creating a Burn backend extension.
+    /// </summary>
+    public abstract class BaseBurnBackendBinderExtension : IBurnBackendBinderExtension
+    {
+        /// <summary>
+        /// Context for use by the extension.
+        /// </summary>
+        protected IBindContext Context { get; private set; }
+
+        /// <summary>
+        /// Messaging for use by the extension.
+        /// </summary>
+        protected IMessaging Messaging { get; private set; }
+
+        /// <summary>
+        /// Backend helper for use by the extension.
+        /// </summary>
+        protected IBurnBackendHelper BackendHelper { get; private set; }
+
+        /// <summary>
+        /// Optional symbol definitions.
+        /// </summary>
+        protected virtual IReadOnlyCollection<IntermediateSymbolDefinition> SymbolDefinitions => Array.Empty<IntermediateSymbolDefinition>();
+
+        /// <summary>
+        /// See <see cref="IBurnBackendBinderExtension.PreBackendBind(IBindContext)"/>
+        /// </summary>
+        public virtual void PreBackendBind(IBindContext context)
+        {
+            this.Context = context;
+            this.Messaging = context.ServiceProvider.GetService<IMessaging>();
+            this.BackendHelper = context.ServiceProvider.GetService<IBurnBackendHelper>();
+        }
+
+        /// <summary>
+        /// See <see cref="IBurnBackendBinderExtension.ResolveRelatedFile(String, String, String, SourceLineNumber)"/>
+        /// </summary>
+        public virtual IResolveFileResult ResolveRelatedFile(string source, string relatedSource, string type, SourceLineNumber sourceLineNumbers)
+        {
+            return null;
+        }
+
+        /// <summary>
+        /// See <see cref="IBurnBackendBinderExtension.SymbolsFinalized(IntermediateSection)"/>
+        /// </summary>
+        public virtual void SymbolsFinalized(IntermediateSection section)
+        {
+        }
+
+        /// <summary>
+        /// See <see cref="IBurnBackendBinderExtension.ResolveUrl(String, String, String, String, String)"/>
+        /// </summary>
+        public virtual string ResolveUrl(string url, string fallbackUrl, string packageId, string payloadId, string fileName)
+        {
+            return null;
+        }
+
+        /// <summary>
+        /// See <see cref="IBurnBackendBinderExtension.TryProcessSymbol(IntermediateSection, IntermediateSymbol)"/>
+        /// </summary>
+        public virtual bool TryProcessSymbol(IntermediateSection section, IntermediateSymbol symbol)
+        {
+            if (this.SymbolDefinitions.Any(t => t == symbol.Definition) &&
+                symbol.Definition.HasTag(BurnConstants.BootstrapperApplicationDataSymbolDefinitionTag))
+            {
+                this.BackendHelper.AddBootstrapperApplicationData(symbol);
+                return true;
+            }
+
+            return false;
+        }
+
+        /// <summary>
+        /// See <see cref="IBurnBackendBinderExtension.PostBackendBind(IBindResult)"/>
+        /// </summary>
+        /// <param name="result"></param>
+        public virtual void PostBackendBind(IBindResult result)
+        {
+        }
+    }
+}
diff --git a/src/api/wix/WixToolset.Extensibility/BaseCompilerExtension.cs b/src/api/wix/WixToolset.Extensibility/BaseCompilerExtension.cs
new file mode 100644
index 00000000..3e185e14
--- /dev/null
+++ b/src/api/wix/WixToolset.Extensibility/BaseCompilerExtension.cs
@@ -0,0 +1,87 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved. Licensed under the Microsoft Reciprocal License. See LICENSE.TXT file in the project root for full license information.
+
+namespace WixToolset.Extensibility
+{
+    using System;
+    using System.Collections.Generic;
+    using System.Xml.Linq;
+    using WixToolset.Data;
+    using WixToolset.Extensibility.Data;
+    using WixToolset.Extensibility.Services;
+
+    /// <summary>
+    /// Base class for creating a compiler extension.
+    /// </summary>
+    public abstract class BaseCompilerExtension : ICompilerExtension
+    {
+        /// <summary>
+        /// Context for use by the extension.
+        /// </summary>
+        protected ICompileContext Context { get; private set; }
+
+        /// <summary>
+        /// Messaging for use by the extension.
+        /// </summary>
+        protected IMessaging Messaging { get; private set; }
+
+        /// <summary>
+        /// ParserHelper for use by the extension.
+        /// </summary>
+        protected IParseHelper ParseHelper { get; private set; }
+
+        /// <summary>
+        /// Gets the schema namespace for this extension.
+        /// </summary>
+        /// <value>Schema namespace supported by this extension.</value>
+        public abstract XNamespace Namespace { get; }
+
+        /// <summary>
+        /// Creates a component key path.
+        /// </summary>
+        protected IComponentKeyPath CreateComponentKeyPath() => this.Context.ServiceProvider.GetService<IComponentKeyPath>();
+
+        /// <summary>
+        /// Called at the beginning of the compilation of a source file.
+        /// </summary>
+        public virtual void PreCompile(ICompileContext context)
+        {
+            this.Context = context;
+
+            this.Messaging = context.ServiceProvider.GetService<IMessaging>();
+
+            this.ParseHelper = context.ServiceProvider.GetService<IParseHelper>();
+        }
+
+        /// <summary>
+        /// See <see cref="ICompilerExtension.ParseAttribute(Intermediate, IntermediateSection, XElement, XAttribute, IDictionary{String, String})"/>
+        /// </summary>
+        public virtual void ParseAttribute(Intermediate intermediate, IntermediateSection section, XElement parentElement, XAttribute attribute, IDictionary<string, string> context)
+        {
+            this.ParseHelper.UnexpectedAttribute(parentElement, attribute);
+        }
+
+        /// <summary>
+        /// See <see cref="ICompilerExtension.ParseElement(Intermediate, IntermediateSection, XElement, XElement, IDictionary{String, String})"/>
+        /// </summary>
+        public virtual void ParseElement(Intermediate intermediate, IntermediateSection section, XElement parentElement, XElement element, IDictionary<string, string> context)
+        {
+            this.ParseHelper.UnexpectedElement(parentElement, element);
+        }
+
+        /// <summary>
+        /// See <see cref="ICompilerExtension.ParsePossibleKeyPathElement(Intermediate, IntermediateSection, XElement, XElement, IDictionary{String, String})"/>
+        /// </summary>
+        public virtual IComponentKeyPath ParsePossibleKeyPathElement(Intermediate intermediate, IntermediateSection section, XElement parentElement, XElement element, IDictionary<string, string> context)
+        {
+            this.ParseElement(intermediate, section, parentElement, element, context);
+            return null;
+        }
+
+        /// <summary>
+        /// Called at the end of the compilation of a source file.
+        /// </summary>
+        public virtual void PostCompile(Intermediate intermediate)
+        {
+        }
+    }
+}
diff --git a/src/api/wix/WixToolset.Extensibility/BaseExtensionCommandLine.cs b/src/api/wix/WixToolset.Extensibility/BaseExtensionCommandLine.cs
new file mode 100644
index 00000000..c716ac7e
--- /dev/null
+++ b/src/api/wix/WixToolset.Extensibility/BaseExtensionCommandLine.cs
@@ -0,0 +1,51 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved. Licensed under the Microsoft Reciprocal License. See LICENSE.TXT file in the project root for full license information.
+
+namespace WixToolset.Extensibility
+{
+    using System;
+    using System.Collections.Generic;
+    using WixToolset.Extensibility.Data;
+    using WixToolset.Extensibility.Services;
+
+    /// <summary>
+    /// Base class for extensions to be able to parse the command-line.
+    /// </summary>
+    public abstract class BaseExtensionCommandLine : IExtensionCommandLine
+    {
+        /// <summary>
+        /// See <see cref="IExtensionCommandLine.CommandLineSwitches" />
+        /// </summary>
+        public virtual IReadOnlyCollection<ExtensionCommandLineSwitch> CommandLineSwitches => Array.Empty<ExtensionCommandLineSwitch>();
+
+        /// <summary>
+        /// See <see cref="IExtensionCommandLine.PostParse" />
+        /// </summary>
+        public virtual void PostParse()
+        {
+        }
+
+        /// <summary>
+        /// See <see cref="IExtensionCommandLine.PreParse" />
+        /// </summary>
+        public virtual void PreParse(ICommandLineContext context)
+        {
+        }
+
+        /// <summary>
+        /// See <see cref="IExtensionCommandLine.TryParseArgument" />
+        /// </summary>
+        public virtual bool TryParseArgument(ICommandLineParser parser, string argument)
+        {
+            return false;
+        }
+
+        /// <summary>
+        /// See <see cref="IExtensionCommandLine.TryParseCommand" />
+        /// </summary>
+        public virtual bool TryParseCommand(ICommandLineParser parser, string argument, out ICommandLineCommand command)
+        {
+            command = null;
+            return false;
+        }
+    }
+}
diff --git a/src/api/wix/WixToolset.Extensibility/BaseExtensionData.cs b/src/api/wix/WixToolset.Extensibility/BaseExtensionData.cs
new file mode 100644
index 00000000..e4a10fd9
--- /dev/null
+++ b/src/api/wix/WixToolset.Extensibility/BaseExtensionData.cs
@@ -0,0 +1,34 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved. Licensed under the Microsoft Reciprocal License. See LICENSE.TXT file in the project root for full license information.
+
+namespace WixToolset.Extensibility
+{
+    using WixToolset.Data;
+
+    /// <summary>
+    /// Base class for creating a resolver extension.
+    /// </summary>
+    public abstract class BaseExtensionData : IExtensionData
+    {
+        /// <summary>
+        /// See <see cref="IExtensionData.DefaultCulture"/>
+        /// </summary>
+        public virtual string DefaultCulture => null;
+
+        /// <summary>
+        /// See <see cref="IExtensionData.GetLibrary"/>
+        /// </summary>
+        public virtual Intermediate GetLibrary(ISymbolDefinitionCreator symbolDefinitions)
+        {
+            return null;
+        }
+
+        /// <summary>
+        /// See <see cref="IExtensionData.TryGetSymbolDefinitionByName"/>
+        /// </summary>
+        public virtual bool TryGetSymbolDefinitionByName(string name, out IntermediateSymbolDefinition symbolDefinition)
+        {
+            symbolDefinition = null;
+            return false;
+        }
+    }
+}
diff --git a/src/api/wix/WixToolset.Extensibility/BaseExtensionFactory.cs b/src/api/wix/WixToolset.Extensibility/BaseExtensionFactory.cs
new file mode 100644
index 00000000..8b6dc566
--- /dev/null
+++ b/src/api/wix/WixToolset.Extensibility/BaseExtensionFactory.cs
@@ -0,0 +1,39 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved. Licensed under the Microsoft Reciprocal License. See LICENSE.TXT file in the project root for full license information.
+
+namespace WixToolset.Extensibility
+{
+    using System;
+    using System.Collections.Generic;
+
+    /// <summary>
+    /// Base class for extension factories.
+    ///
+    /// Implementations may request an IWixToolsetCoreServiceProvider at instantiation by having a single parameter constructor for it.
+    /// </summary>
+    public abstract class BaseExtensionFactory : IExtensionFactory
+    {
+        /// <summary>
+        /// The extension types of the WiX extension.
+        /// </summary>
+        protected abstract IReadOnlyCollection<Type> ExtensionTypes { get; }
+
+        /// <summary>
+        /// See <see cref="IExtensionFactory.TryCreateExtension(Type, out object)"/>
+        /// </summary>
+        public virtual bool TryCreateExtension(Type extensionType, out object extension)
+        {
+            extension = null;
+
+            foreach (var type in this.ExtensionTypes)
+            {
+                if (extensionType.IsAssignableFrom(type))
+                {
+                    extension = Activator.CreateInstance(type);
+                    break;
+                }
+            }
+
+            return extension != null;
+        }
+    }
+}
diff --git a/src/api/wix/WixToolset.Extensibility/BaseLayoutExtension.cs b/src/api/wix/WixToolset.Extensibility/BaseLayoutExtension.cs
new file mode 100644
index 00000000..21b932ff
--- /dev/null
+++ b/src/api/wix/WixToolset.Extensibility/BaseLayoutExtension.cs
@@ -0,0 +1,62 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved. Licensed under the Microsoft Reciprocal License. See LICENSE.TXT file in the project root for full license information.
+
+namespace WixToolset.Extensibility
+{
+    using WixToolset.Extensibility.Data;
+    using WixToolset.Extensibility.Services;
+
+    /// <summary>
+    /// Base class for creating a resolver extension.
+    /// </summary>
+    public abstract class BaseLayoutExtension : ILayoutExtension
+    {
+        /// <summary>
+        /// Context for use by the extension.
+        /// </summary>
+        protected ILayoutContext Context { get; private set; }
+
+        /// <summary>
+        /// Messaging for use by the extension.
+        /// </summary>
+        protected IMessaging Messaging { get; private set; }
+
+        /// <summary>
+        /// Called at the beginning of layout.
+        /// </summary>
+        public virtual void PreLayout(ILayoutContext context)
+        {
+            this.Context = context;
+
+            this.Messaging = context.ServiceProvider.GetService<IMessaging>();
+        }
+
+        /// <summary>
+        /// See <see cref="ILayoutExtension.CopyFile(string, string)"/>
+        /// </summary>
+        /// <param name="source"></param>
+        /// <param name="destination"></param>
+        /// <returns></returns>
+        public virtual bool CopyFile(string source, string destination)
+        {
+            return false;
+        }
+
+        /// <summary>
+        /// See <see cref="ILayoutExtension.MoveFile(string, string)"/>
+        /// </summary>
+        /// <param name="source"></param>
+        /// <param name="destination"></param>
+        /// <returns></returns>
+        public virtual bool MoveFile(string source, string destination)
+        {
+            return false;
+        }
+
+        /// <summary>
+        /// Called at the end of ayout.
+        /// </summary>
+        public virtual void PostLayout()
+        {
+        }
+    }
+}
diff --git a/src/api/wix/WixToolset.Extensibility/BaseLibrarianExtension.cs b/src/api/wix/WixToolset.Extensibility/BaseLibrarianExtension.cs
new file mode 100644
index 00000000..cbc9e4ba
--- /dev/null
+++ b/src/api/wix/WixToolset.Extensibility/BaseLibrarianExtension.cs
@@ -0,0 +1,71 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved. Licensed under the Microsoft Reciprocal License. See LICENSE.TXT file in the project root for full license information.
+
+namespace WixToolset.Extensibility
+{
+    using System.Collections.Generic;
+    using WixToolset.Data;
+    using WixToolset.Extensibility.Data;
+    using WixToolset.Extensibility.Services;
+
+    /// <summary>
+    /// Base class for creating a librarian extension.
+    /// </summary>
+    public abstract class BaseLibrarianExtension : ILibrarianExtension
+    {
+        /// <summary>
+        /// Context for use by the extension.
+        /// </summary>
+        protected ILibraryContext Context { get; private set; }
+
+        /// <summary>
+        /// Messaging for use by the extension.
+        /// </summary>
+        protected IMessaging Messaging { get; private set; }
+
+        /// <summary>
+        /// Called at the beginning of combining.
+        /// </summary>
+        /// <param name="context">Librarian context.</param>
+        public virtual void PreCombine(ILibraryContext context)
+        {
+            this.Context = context;
+
+            this.Messaging = context.ServiceProvider.GetService<IMessaging>();
+        }
+
+        /// <summary>
+        /// Resolves a path to a file path on disk.
+        /// </summary>
+        /// <param name="sourceLineNumber">Source line number for the path to resolve.</param>
+        /// <param name="symbolDefinition">Symbol related to the path to resolve.</param>
+        /// <param name="path">Path to resolve.</param>
+        /// <returns>Optional resolved file result.</returns>
+        public virtual IResolveFileResult ResolveFile(SourceLineNumber sourceLineNumber, IntermediateSymbolDefinition symbolDefinition, string path)
+        {
+            return null;
+        }
+
+        /// <summary>
+        /// Called at the end of combining.
+        /// </summary>
+        /// <param name="library">Combined library intermediate.</param>
+        public virtual void PostCombine(Intermediate library)
+        {
+        }
+
+        /// <summary>
+        /// Creates an IResolveFileResult.
+        /// </summary>
+        /// <param name="path">Optional resolved path to file.</param>
+        /// <param name="checkedPaths">Optional collection of paths checked for the file.</param>
+        /// <returns>Resolved file result.</returns>
+        protected IResolveFileResult CreateResolveFileResult(string path = null, IReadOnlyCollection<string> checkedPaths = null)
+        {
+            var result = this.Context.ServiceProvider.GetService<IResolveFileResult>();
+            result.Path = path;
+            result.CheckedPaths = checkedPaths;
+
+            return result;
+        }
+    }
+}
diff --git a/src/api/wix/WixToolset.Extensibility/BaseLinkerExtension.cs b/src/api/wix/WixToolset.Extensibility/BaseLinkerExtension.cs
new file mode 100644
index 00000000..91aefc2f
--- /dev/null
+++ b/src/api/wix/WixToolset.Extensibility/BaseLinkerExtension.cs
@@ -0,0 +1,41 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved. Licensed under the Microsoft Reciprocal License. See LICENSE.TXT file in the project root for full license information.
+
+namespace WixToolset.Extensibility
+{
+    using WixToolset.Data;
+    using WixToolset.Extensibility.Data;
+    using WixToolset.Extensibility.Services;
+
+    /// <summary>
+    /// Base class for creating a linker extension.
+    /// </summary>
+    public abstract class BaseLinkerExtension : ILinkerExtension
+    {
+        /// <summary>
+        /// Context for use by the extension.
+        /// </summary>
+        protected ILinkContext Context { get; private set; }
+
+        /// <summary>
+        /// Messaging for use by the extension.
+        /// </summary>
+        protected IMessaging Messaging { get; private set; }
+
+        /// <summary>
+        /// Called at the beginning of the linking.
+        /// </summary>
+        public virtual void PreLink(ILinkContext context)
+        {
+            this.Context = context;
+
+            this.Messaging = context.ServiceProvider.GetService<IMessaging>();
+        }
+
+        /// <summary>
+        /// Called at the end of the linking.
+        /// </summary>
+        public virtual void PostLink(Intermediate intermediate)
+        {
+        }
+    }
+}
diff --git a/src/api/wix/WixToolset.Extensibility/BasePreprocessorExtension.cs b/src/api/wix/WixToolset.Extensibility/BasePreprocessorExtension.cs
new file mode 100644
index 00000000..b9a856ec
--- /dev/null
+++ b/src/api/wix/WixToolset.Extensibility/BasePreprocessorExtension.cs
@@ -0,0 +1,91 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved. Licensed under the Microsoft Reciprocal License. See LICENSE.TXT file in the project root for full license information.
+
+namespace WixToolset.Extensibility
+{
+    using System.Xml.Linq;
+    using WixToolset.Extensibility.Data;
+    using WixToolset.Extensibility.Services;
+
+    /// <summary>
+    /// Base class for creating a preprocessor extension.
+    /// </summary>
+    public abstract class BasePreprocessorExtension : IPreprocessorExtension
+    {
+        /// <summary>
+        /// Context for use by the extension.
+        /// </summary>
+        protected IPreprocessContext Context { get; private set; }
+
+        /// <summary>
+        /// Messaging for use by the extension.
+        /// </summary>
+        protected IMessaging Messaging { get; private set; }
+
+        /// <summary>
+        /// PreprocessHelper for use by the extension.
+        /// </summary>
+        protected IPreprocessHelper PreprocessHelper { get; private set; }
+
+        /// <summary>
+        /// Gets or sets the variable prefixes for the extension.
+        /// </summary>
+        /// <value>The variable prefixes for the extension.</value>
+        public string[] Prefixes { get; protected set; }
+
+        /// <summary>
+        /// Called at the beginning of the preprocessing of a source file.
+        /// </summary>
+        public virtual void PrePreprocess(IPreprocessContext context)
+        {
+            this.Context = context;
+
+            this.Messaging = context.ServiceProvider.GetService<IMessaging>();
+
+            this.PreprocessHelper = context.ServiceProvider.GetService<IPreprocessHelper>();
+        }
+
+        /// <summary>
+        /// Gets the value of a variable whose prefix matches the extension.
+        /// </summary>
+        /// <param name="prefix">The prefix of the variable to be processed by the extension.</param>
+        /// <param name="name">The name of the variable.</param>
+        /// <returns>The value of the variable or null if the variable is undefined.</returns>
+        public virtual string GetVariableValue(string prefix, string name)
+        {
+            return null;
+        }
+
+        /// <summary>
+        /// Evaluates a function defined in the extension.
+        /// </summary>
+        /// <param name="prefix">The prefix of the function to be processed by the extension.</param>
+        /// <param name="function">The name of the function.</param>
+        /// <param name="args">The list of arguments.</param>
+        /// <returns>The value of the function or null if the function is not defined.</returns>
+        public virtual string EvaluateFunction(string prefix, string function, string[] args)
+        {
+            return null;
+        }
+
+        /// <summary>
+        /// Processes a pragma defined in the extension.
+        /// </summary>
+        /// <param name="prefix">The prefix of the pragma to be processed by the extension.</param>
+        /// <param name="pragma">The name of the pragma.</param>
+        /// <param name="args">The pragma's arguments.</param>
+        /// <param name="parent">The parent node of the pragma.</param>
+        /// <returns>false if the pragma is not defined.</returns>
+        /// <comments>Don't return false for any condition except for unrecognized pragmas. Throw errors that are fatal to the compile. use core.OnMessage for warnings and messages.</comments>
+        public virtual bool ProcessPragma(string prefix, string pragma, string args, XContainer parent)
+        {
+            return false;
+        }
+
+        /// <summary>
+        /// Called at the end of the preprocessing of a source file.
+        /// </summary>
+        public virtual void PostPreprocess(IPreprocessResult result)
+        {
+        }
+    }
+}
diff --git a/src/api/wix/WixToolset.Extensibility/BaseResolverExtension.cs b/src/api/wix/WixToolset.Extensibility/BaseResolverExtension.cs
new file mode 100644
index 00000000..72dc5c41
--- /dev/null
+++ b/src/api/wix/WixToolset.Extensibility/BaseResolverExtension.cs
@@ -0,0 +1,59 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved. Licensed under the Microsoft Reciprocal License. See LICENSE.TXT file in the project root for full license information.
+
+namespace WixToolset.Extensibility
+{
+    using WixToolset.Data;
+    using WixToolset.Extensibility.Data;
+    using WixToolset.Extensibility.Services;
+
+    /// <summary>
+    /// Base class for creating a resolver extension.
+    /// </summary>
+    public abstract class BaseResolverExtension : IResolverExtension
+    {
+        /// <summary>
+        /// Context for use by the extension.
+        /// </summary>
+        protected IResolveContext Context { get; private set; }
+
+        /// <summary>
+        /// Messaging for use by the extension.
+        /// </summary>
+        protected IMessaging Messaging { get; private set; }
+
+        /// <summary>
+        /// Creates a resolve file result.
+        /// </summary>
+        protected IResolveFileResult CreateResolveFileResult() => this.Context.ServiceProvider.GetService<IResolveFileResult>();
+
+        /// <summary>
+        /// Called at the beginning of the resolving variables and files.
+        /// </summary>
+        public virtual void PreResolve(IResolveContext context)
+        {
+            this.Context = context;
+
+            this.Messaging = context.ServiceProvider.GetService<IMessaging>();
+        }
+
+        /// <summary>
+        /// See <see cref="IResolverExtension.ResolveFile(string, IntermediateSymbolDefinition, SourceLineNumber, BindStage)"/>
+        /// </summary>
+        /// <param name="source"></param>
+        /// <param name="symbolDefinition"></param>
+        /// <param name="sourceLineNumbers"></param>
+        /// <param name="bindStage"></param>
+        /// <returns></returns>
+        public virtual IResolveFileResult ResolveFile(string source, IntermediateSymbolDefinition symbolDefinition, SourceLineNumber sourceLineNumbers, BindStage bindStage)
+        {
+            return null;
+        }
+
+        /// <summary>
+        /// Called at the end of resolve.
+        /// </summary>
+        public virtual void PostResolve(IResolveResult result)
+        {
+        }
+    }
+}
diff --git a/src/api/wix/WixToolset.Extensibility/BaseWindowsInstallerBackendBinderExtension.cs b/src/api/wix/WixToolset.Extensibility/BaseWindowsInstallerBackendBinderExtension.cs
new file mode 100644
index 00000000..ffff186b
--- /dev/null
+++ b/src/api/wix/WixToolset.Extensibility/BaseWindowsInstallerBackendBinderExtension.cs
@@ -0,0 +1,93 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved. Licensed under the Microsoft Reciprocal License. See LICENSE.TXT file in the project root for full license information.
+
+namespace WixToolset.Extensibility
+{
+    using System;
+    using System.Collections.Generic;
+    using System.Linq;
+    using WixToolset.Data;
+    using WixToolset.Data.Symbols;
+    using WixToolset.Data.WindowsInstaller;
+    using WixToolset.Extensibility.Data;
+    using WixToolset.Extensibility.Services;
+
+    /// <summary>
+    /// Base class for creating a preprocessor extension.
+    /// </summary>
+    public abstract class BaseWindowsInstallerBackendBinderExtension : IWindowsInstallerBackendBinderExtension
+    {
+        /// <summary>
+        /// Context for use by the extension.
+        /// </summary>
+        protected IBindContext Context { get; private set; }
+
+        /// <summary>
+        /// Messaging for use by the extension.
+        /// </summary>
+        protected IMessaging Messaging { get; private set; }
+
+        /// <summary>
+        /// Backend helper for use by the extension.
+        /// </summary>
+        protected IWindowsInstallerBackendHelper BackendHelper { get; private set; }
+
+        /// <summary>
+        /// Optional table definitions.
+        /// </summary>
+        public virtual IReadOnlyCollection<TableDefinition> TableDefinitions => Array.Empty<TableDefinition>();
+
+        /// <summary>
+        /// Creates a resolved cabinet result.
+        /// </summary>
+        protected IResolvedCabinet CreateResolvedCabinet() => this.Context.ServiceProvider.GetService<IResolvedCabinet>();
+
+        /// <summary>
+        /// See <see cref="IWindowsInstallerBackendBinderExtension.PreBackendBind(IBindContext)"/>
+        /// </summary>
+        public virtual void PreBackendBind(IBindContext context)
+        {
+            this.Context = context;
+
+            this.Messaging = context.ServiceProvider.GetService<IMessaging>();
+
+            this.BackendHelper = context.ServiceProvider.GetService<IWindowsInstallerBackendHelper>();
+        }
+
+        /// <summary>
+        /// See <see cref="IWindowsInstallerBackendBinderExtension.SymbolsFinalized(IntermediateSection)"/>
+        /// </summary>
+        public virtual void SymbolsFinalized(IntermediateSection section)
+        {
+        }
+
+        /// <summary>
+        /// See <see cref="IWindowsInstallerBackendBinderExtension.PreBackendBind(IBindContext)"/>
+        /// </summary>
+        public virtual IResolvedCabinet ResolveCabinet(string cabinetPath, IEnumerable<IBindFileWithPath> files) => null;
+
+        /// <summary>
+        /// See <see cref="IWindowsInstallerBackendBinderExtension.PreBackendBind(IBindContext)"/>
+        /// </summary>
+        public virtual string ResolveMedia(MediaSymbol mediaRow, string mediaLayoutDirectory, string layoutDirectory) => null;
+
+        /// <summary>
+        /// See <see cref="IWindowsInstallerBackendBinderExtension.TryProcessSymbol(IntermediateSection, IntermediateSymbol, WindowsInstallerData, TableDefinitionCollection)"/>
+        /// </summary>
+        public virtual bool TryProcessSymbol(IntermediateSection section, IntermediateSymbol symbol, WindowsInstallerData data, TableDefinitionCollection tableDefinitions)
+        {
+            if (this.TableDefinitions.Any(t => t.SymbolDefinition == symbol.Definition))
+            {
+                return this.BackendHelper.TryAddSymbolToMatchingTableDefinitions(section, symbol, data, tableDefinitions);
+            }
+
+            return false;
+        }
+
+        /// <summary>
+        /// See <see cref="IWindowsInstallerBackendBinderExtension.PreBackendBind(IBindContext)"/>
+        /// </summary>
+        public virtual void PostBackendBind(IBindResult result)
+        {
+        }
+    }
+}
diff --git a/src/api/wix/WixToolset.Extensibility/CompilerConstants.cs b/src/api/wix/WixToolset.Extensibility/CompilerConstants.cs
new file mode 100644
index 00000000..73ff685c
--- /dev/null
+++ b/src/api/wix/WixToolset.Extensibility/CompilerConstants.cs
@@ -0,0 +1,42 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved. Licensed under the Microsoft Reciprocal License. See LICENSE.TXT file in the project root for full license information.
+
+namespace WixToolset.Extensibility
+{
+    using System;
+
+    /// <summary>
+    /// Constants used by compiler.
+    /// </summary>
+    public static class CompilerConstants
+    {
+        /// <summary>
+        /// 
+        /// </summary>
+        public const int IntegerNotSet = int.MinValue;
+
+        /// <summary>
+        /// 
+        /// </summary>
+        public const int IllegalInteger = int.MinValue + 1;
+
+        /// <summary>
+        /// 
+        /// </summary>
+        public const long LongNotSet = long.MinValue;
+
+        /// <summary>
+        /// 
+        /// </summary>
+        public const long IllegalLong = long.MinValue + 1;
+
+        /// <summary>
+        /// 
+        /// </summary>
+        public const string IllegalGuid = "IllegalGuid";
+
+        /// <summary>
+        /// 
+        /// </summary>
+        public static readonly Version IllegalVersion = new Version(Int32.MaxValue, Int32.MaxValue, Int32.MaxValue, Int32.MaxValue);
+    }
+}
diff --git a/src/api/wix/WixToolset.Extensibility/Data/BindStage.cs b/src/api/wix/WixToolset.Extensibility/Data/BindStage.cs
new file mode 100644
index 00000000..a690a896
--- /dev/null
+++ b/src/api/wix/WixToolset.Extensibility/Data/BindStage.cs
@@ -0,0 +1,25 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved. Licensed under the Microsoft Reciprocal License. See LICENSE.TXT file in the project root for full license information.
+
+namespace WixToolset.Extensibility.Data
+{
+    /// <summary>
+    /// 
+    /// </summary>
+    public enum BindStage
+    {
+        /// <summary>
+        /// Normal binding
+        /// </summary>
+        Normal,
+
+        /// <summary>
+        /// Bind the file path of the target build file
+        /// </summary>
+        Target,
+
+        /// <summary>
+        /// Bind the file path of the updated build file
+        /// </summary>
+        Updated,
+    }
+}
diff --git a/src/api/wix/WixToolset.Extensibility/Data/BurnPlatforms.cs b/src/api/wix/WixToolset.Extensibility/Data/BurnPlatforms.cs
new file mode 100644
index 00000000..ab4beb7d
--- /dev/null
+++ b/src/api/wix/WixToolset.Extensibility/Data/BurnPlatforms.cs
@@ -0,0 +1,25 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved. Licensed under the Microsoft Reciprocal License. See LICENSE.TXT file in the project root for full license information.
+
+namespace WixToolset.Extensibility.Data
+{
+    using System;
+
+    /// <summary>
+    /// Platforms that have been supported by Burn.
+    /// </summary>
+    [Flags]
+    public enum BurnPlatforms
+    {
+        /// <summary>Not specified.</summary>
+        None = 0,
+
+        /// <summary>x86.</summary>
+        X86 = 0x1,
+
+        /// <summary>x64.</summary>
+        X64 = 0x2,
+
+        /// <summary>arm64.</summary>
+        ARM64 = 0x4,
+    }
+}
diff --git a/src/api/wix/WixToolset.Extensibility/Data/CabinetBuildOption.cs b/src/api/wix/WixToolset.Extensibility/Data/CabinetBuildOption.cs
new file mode 100644
index 00000000..f9938814
--- /dev/null
+++ b/src/api/wix/WixToolset.Extensibility/Data/CabinetBuildOption.cs
@@ -0,0 +1,25 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved. Licensed under the Microsoft Reciprocal License. See LICENSE.TXT file in the project root for full license information.
+
+namespace WixToolset.Extensibility.Data
+{
+    /// <summary>
+    /// Options for building the cabinet.
+    /// </summary>
+    public enum CabinetBuildOption
+    {
+        /// <summary>
+        /// Build the cabinet and move it to the target location.
+        /// </summary>
+        BuildAndMove,
+
+        /// <summary>
+        /// Build the cabinet and copy it to the target location.
+        /// </summary>
+        BuildAndCopy,
+
+        /// <summary>
+        /// Just copy the cabinet to the target location.
+        /// </summary>
+        Copy
+    }
+}
diff --git a/src/api/wix/WixToolset.Extensibility/Data/CustomActionPlatforms.cs b/src/api/wix/WixToolset.Extensibility/Data/CustomActionPlatforms.cs
new file mode 100644
index 00000000..eea8a419
--- /dev/null
+++ b/src/api/wix/WixToolset.Extensibility/Data/CustomActionPlatforms.cs
@@ -0,0 +1,25 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved. Licensed under the Microsoft Reciprocal License. See LICENSE.TXT file in the project root for full license information.
+
+namespace WixToolset.Extensibility.Data
+{
+    using System;
+
+    /// <summary>
+    /// Platforms supported by custom actions.
+    /// </summary>
+    [Flags]
+    public enum CustomActionPlatforms
+    {
+        /// <summary>Not specified.</summary>
+        None = 0,
+
+        /// <summary>x86.</summary>
+        X86 = 0x1,
+
+        /// <summary>x64.</summary>
+        X64 = 0x2,
+
+        /// <summary>arm64.</summary>
+        ARM64 = 0x4,
+    }
+}
diff --git a/src/api/wix/WixToolset.Extensibility/Data/ExtensionCommandLineSwitch.cs b/src/api/wix/WixToolset.Extensibility/Data/ExtensionCommandLineSwitch.cs
new file mode 100644
index 00000000..14b5dabb
--- /dev/null
+++ b/src/api/wix/WixToolset.Extensibility/Data/ExtensionCommandLineSwitch.cs
@@ -0,0 +1,20 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved. Licensed under the Microsoft Reciprocal License. See LICENSE.TXT file in the project root for full license information.
+
+namespace WixToolset.Extensibility.Data
+{
+    /// <summary>
+    /// A command line option.
+    /// </summary>
+    public struct ExtensionCommandLineSwitch
+    {
+        /// <summary>
+        /// 
+        /// </summary>
+        public string Switch { get; set; }
+
+        /// <summary>
+        /// 
+        /// </summary>
+        public string Description { get; set; }
+    }
+}
diff --git a/src/api/wix/WixToolset.Extensibility/Data/IBindContext.cs b/src/api/wix/WixToolset.Extensibility/Data/IBindContext.cs
new file mode 100644
index 00000000..d0c65683
--- /dev/null
+++ b/src/api/wix/WixToolset.Extensibility/Data/IBindContext.cs
@@ -0,0 +1,120 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved. Licensed under the Microsoft Reciprocal License. See LICENSE.TXT file in the project root for full license information.
+
+namespace WixToolset.Extensibility.Data
+{
+    using System;
+    using System.Collections.Generic;
+    using System.Threading;
+    using WixToolset.Data;
+
+    /// <summary>
+    /// Bind context.
+    /// </summary>
+    public interface IBindContext
+    {
+        /// <summary>
+        /// Service provider.
+        /// </summary>
+        IServiceProvider ServiceProvider { get; }
+
+        /// <summary>
+        /// Counnt of threads to use in cabbing.
+        /// </summary>
+        int CabbingThreadCount { get; set; }
+
+        /// <summary>
+        /// Cabinet cache path.
+        /// </summary>
+        string CabCachePath { get; set; }
+
+        /// <summary>
+        /// Default compression level.
+        /// </summary>
+        CompressionLevel? DefaultCompressionLevel { get; set; }
+
+        /// <summary>
+        /// Delayed fields that need to be resolved again.
+        /// </summary>
+        IReadOnlyCollection<IDelayedField> DelayedFields { get; set; }
+
+        /// <summary>
+        /// Embedded files to extract.
+        /// </summary>
+        IReadOnlyCollection<IExpectedExtractFile> ExpectedEmbeddedFiles { get; set; }
+
+        /// <summary>
+        /// Binder extensions.
+        /// </summary>
+        IReadOnlyCollection<IBinderExtension> Extensions { get; set; }
+
+        /// <summary>
+        /// File system extensions.
+        /// </summary>
+        IReadOnlyCollection<IFileSystemExtension> FileSystemExtensions { get; set; }
+
+        /// <summary>
+        /// Set of ICEs to execute.
+        /// </summary>
+        IReadOnlyCollection<string> Ices { get; set; }
+
+        /// <summary>
+        /// Intermedaite folder.
+        /// </summary>
+        string IntermediateFolder { get; set; }
+
+        /// <summary>
+        /// Intermediate representation to bind.
+        /// </summary>
+        Intermediate IntermediateRepresentation { get; set; }
+
+        /// <summary>
+        /// Output path to bind to.
+        /// </summary>
+        string OutputPath { get; set; }
+
+        /// <summary>
+        /// Type of PDB to create.
+        /// </summary>
+        PdbType PdbType { get; set; }
+
+        /// <summary>
+        /// Output path for PDB.
+        /// </summary>
+        string PdbPath { get; set; }
+
+        /// <summary>
+        /// Codepage from resolve.
+        /// </summary>
+        int? ResolvedCodepage { get; set; }
+
+        /// <summary>
+        /// Summary information codepage from resolve.
+        /// </summary>
+        int? ResolvedSummaryInformationCodepage { get; set; }
+
+        /// <summary>
+        /// LCID from resolve.
+        /// </summary>
+        int? ResolvedLcid { get; set; }
+
+        /// <summary>
+        /// Set of ICEs to skip.
+        /// </summary>
+        IReadOnlyCollection<string> SuppressIces { get; set; }
+
+        /// <summary>
+        /// Skip all ICEs.
+        /// </summary>
+        bool SuppressValidation { get; set; }
+
+        /// <summary>
+        /// Skip creation of output.
+        /// </summary>
+        bool SuppressLayout { get; set; }
+
+        /// <summary>
+        /// Cancellation token.
+        /// </summary>
+        CancellationToken CancellationToken { get; set; }
+    }
+}
diff --git a/src/api/wix/WixToolset.Extensibility/Data/IBindFileWithPath.cs b/src/api/wix/WixToolset.Extensibility/Data/IBindFileWithPath.cs
new file mode 100644
index 00000000..69036113
--- /dev/null
+++ b/src/api/wix/WixToolset.Extensibility/Data/IBindFileWithPath.cs
@@ -0,0 +1,12 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved. Licensed under the Microsoft Reciprocal License. See LICENSE.TXT file in the project root for full license information.
+
+namespace WixToolset.Extensibility.Data
+{
+#pragma warning disable 1591 // TODO: add documentation
+    public interface IBindFileWithPath
+    {
+        string Id { get; set; }
+
+        string Path { get; set; }
+    }
+}
diff --git a/src/api/wix/WixToolset.Extensibility/Data/IBindPath.cs b/src/api/wix/WixToolset.Extensibility/Data/IBindPath.cs
new file mode 100644
index 00000000..46895e89
--- /dev/null
+++ b/src/api/wix/WixToolset.Extensibility/Data/IBindPath.cs
@@ -0,0 +1,25 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved. Licensed under the Microsoft Reciprocal License. See LICENSE.TXT file in the project root for full license information.
+
+namespace WixToolset.Extensibility.Data
+{
+    /// <summary>
+    /// Interface for a bind path.
+    /// </summary>
+    public interface IBindPath
+    {
+        /// <summary>
+        /// Name of the bind path or String.Empty if the path is unnamed.
+        /// </summary>
+        string Name { get; set; }
+
+        /// <summary>
+        /// Path for the bind path.
+        /// </summary>
+        string Path { get; set; }
+
+        /// <summary>
+        /// Stage for the bind path.
+        /// </summary>
+        BindStage Stage { get; set; }
+    }
+}
diff --git a/src/api/wix/WixToolset.Extensibility/Data/IBindResult.cs b/src/api/wix/WixToolset.Extensibility/Data/IBindResult.cs
new file mode 100644
index 00000000..3738ef17
--- /dev/null
+++ b/src/api/wix/WixToolset.Extensibility/Data/IBindResult.cs
@@ -0,0 +1,29 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved. Licensed under the Microsoft Reciprocal License. See LICENSE.TXT file in the project root for full license information.
+
+namespace WixToolset.Extensibility.Data
+{
+    using System;
+    using System.Collections.Generic;
+    using WixToolset.Data;
+
+    /// <summary>
+    /// Result of bind operation.
+    /// </summary>
+    public interface IBindResult : IDisposable
+    {
+        /// <summary>
+        /// Collection of file transfers to complete.
+        /// </summary>
+        IReadOnlyCollection<IFileTransfer> FileTransfers { get; set; }
+
+        /// <summary>
+        /// Collection of files tracked during binding.
+        /// </summary>
+        IReadOnlyCollection<ITrackedFile> TrackedFiles { get; set; }
+
+        /// <summary>
+        /// Output of binding.
+        /// </summary>
+        WixOutput Wixout { get; set; }
+    }
+}
diff --git a/src/api/wix/WixToolset.Extensibility/Data/ICommandLineArguments.cs b/src/api/wix/WixToolset.Extensibility/Data/ICommandLineArguments.cs
new file mode 100644
index 00000000..32ee4c09
--- /dev/null
+++ b/src/api/wix/WixToolset.Extensibility/Data/ICommandLineArguments.cs
@@ -0,0 +1,39 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved. Licensed under the Microsoft Reciprocal License. See LICENSE.TXT file in the project root for full license information.
+
+namespace WixToolset.Extensibility.Data
+{
+    using WixToolset.Extensibility.Services;
+
+    /// <summary>
+    /// Parsed command-line arguments.
+    /// </summary>
+    public interface ICommandLineArguments
+    {
+#pragma warning disable 1591 // TODO: add documentation
+        string[] OriginalArguments { get; set; }
+
+        string[] Arguments { get; set; }
+
+        string[] Extensions { get; set; }
+
+        string ErrorArgument { get; set; }
+
+        /// <summary>
+        /// Populate this argument from a string.
+        /// </summary>
+        /// <param name="commandLine">String to parse.</param>
+        void Populate(string commandLine);
+
+        /// <summary>
+        /// Populate this argument from array of strings.
+        /// </summary>
+        /// <param name="args">Array of strings.</param>
+        void Populate(string[] args);
+
+        /// <summary>
+        /// Parses this arguments after it is populated.
+        /// </summary>
+        /// <returns>Parser for this arguments.</returns>
+        ICommandLineParser Parse();
+    }
+}
diff --git a/src/api/wix/WixToolset.Extensibility/Data/ICommandLineCommand.cs b/src/api/wix/WixToolset.Extensibility/Data/ICommandLineCommand.cs
new file mode 100644
index 00000000..b03a18f4
--- /dev/null
+++ b/src/api/wix/WixToolset.Extensibility/Data/ICommandLineCommand.cs
@@ -0,0 +1,39 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved. Licensed under the Microsoft Reciprocal License. See LICENSE.TXT file in the project root for full license information.
+
+namespace WixToolset.Extensibility.Data
+{
+    using System.Threading;
+    using System.Threading.Tasks;
+    using WixToolset.Extensibility.Services;
+
+    /// <summary>
+    /// Custom command.
+    /// </summary>
+    public interface ICommandLineCommand
+    {
+        /// <summary>
+        /// Indicates the command-line should show the command-line logo.
+        /// </summary>
+        bool ShowLogo { get; }
+
+        /// <summary>
+        /// Indicates the command-line parsing can stop.
+        /// </summary>
+        bool StopParsing { get; }
+
+        /// <summary>
+        /// Executes the command.
+        /// </summary>
+        /// <param name="cancellationToken">Cancellation token.</param>
+        /// <returns>Exit code for the command.</returns>
+        Task<int> ExecuteAsync(CancellationToken cancellationToken);
+
+        /// <summary>
+        /// Allows the command to parse command-line arguments.
+        /// </summary>
+        /// <param name="parser">Parser to help parse the argument and additional arguments.</param>
+        /// <param name="argument">Argument to parse.</param>
+        /// <returns>True if the argument is recognized; otherwise false to allow another extension to process it.</returns>
+        bool TryParseArgument(ICommandLineParser parser, string argument); 
+    }
+}
diff --git a/src/api/wix/WixToolset.Extensibility/Data/ICommandLineContext.cs b/src/api/wix/WixToolset.Extensibility/Data/ICommandLineContext.cs
new file mode 100644
index 00000000..d8c9469e
--- /dev/null
+++ b/src/api/wix/WixToolset.Extensibility/Data/ICommandLineContext.cs
@@ -0,0 +1,17 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved. Licensed under the Microsoft Reciprocal License. See LICENSE.TXT file in the project root for full license information.
+
+namespace WixToolset.Extensibility.Data
+{
+    using System;
+    using WixToolset.Extensibility.Services;
+
+#pragma warning disable 1591 // TODO: add documentation
+    public interface ICommandLineContext
+    {
+        IServiceProvider ServiceProvider { get; }
+
+        IExtensionManager ExtensionManager { get; set; }
+
+        ICommandLineArguments Arguments { get; set; }
+    }
+}
diff --git a/src/api/wix/WixToolset.Extensibility/Data/ICompileContext.cs b/src/api/wix/WixToolset.Extensibility/Data/ICompileContext.cs
new file mode 100644
index 00000000..2ee8f2a1
--- /dev/null
+++ b/src/api/wix/WixToolset.Extensibility/Data/ICompileContext.cs
@@ -0,0 +1,52 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved. Licensed under the Microsoft Reciprocal License. See LICENSE.TXT file in the project root for full license information.
+
+namespace WixToolset.Extensibility.Data
+{
+    using System;
+    using System.Collections.Generic;
+    using System.Threading;
+    using System.Xml.Linq;
+    using WixToolset.Data;
+
+    /// <summary>
+    /// Context provided to the compiler.
+    /// </summary>
+    public interface ICompileContext
+    {
+        /// <summary>
+        /// Service provider made available to the compiler and its extensions.
+        /// </summary>
+        IServiceProvider ServiceProvider { get; }
+
+        /// <summary>
+        /// Unique identifier for the compilation.
+        /// </summary>
+        string CompilationId { get; set; }
+
+        /// <summary>
+        /// Set of extensions provided to the compiler.
+        /// </summary>
+        IReadOnlyCollection<ICompilerExtension> Extensions { get; set; }
+
+        /// <summary>
+        /// Gets or sets the platform which the compiler will use when defaulting 64-bit attributes and elements.
+        /// </summary>
+        /// <value>The platform which the compiler will use when defaulting 64-bit attributes and elements.</value>
+        Platform Platform { get; set; }
+
+        /// <summary>
+        /// Calculates whether the target platform for the compilation is 64-bit or not.
+        /// </summary>
+        bool IsCurrentPlatform64Bit { get; }
+
+        /// <summary>
+        /// Source document being compiled.
+        /// </summary>
+        XDocument Source { get; set; }
+
+        /// <summary>
+        /// Cancellation token to abort cancellation.
+        /// </summary>
+        CancellationToken CancellationToken { get; set; }
+    }
+}
diff --git a/src/api/wix/WixToolset.Extensibility/Data/IComponentKeyPath.cs b/src/api/wix/WixToolset.Extensibility/Data/IComponentKeyPath.cs
new file mode 100644
index 00000000..2de9c028
--- /dev/null
+++ b/src/api/wix/WixToolset.Extensibility/Data/IComponentKeyPath.cs
@@ -0,0 +1,14 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved. Licensed under the Microsoft Reciprocal License. See LICENSE.TXT file in the project root for full license information.
+
+namespace WixToolset.Extensibility.Data
+{
+#pragma warning disable 1591 // TODO: add documentation
+    public interface IComponentKeyPath
+    {
+        bool Explicit { get; set; }
+
+        string Id { get; set; }
+
+        PossibleKeyPathType Type { get; set; }
+    }
+}
diff --git a/src/api/wix/WixToolset.Extensibility/Data/IDecompileContext.cs b/src/api/wix/WixToolset.Extensibility/Data/IDecompileContext.cs
new file mode 100644
index 00000000..fe7d0465
--- /dev/null
+++ b/src/api/wix/WixToolset.Extensibility/Data/IDecompileContext.cs
@@ -0,0 +1,59 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved. Licensed under the Microsoft Reciprocal License. See LICENSE.TXT file in the project root for full license information.
+
+namespace WixToolset.Extensibility.Data
+{
+    using System;
+    using System.Collections.Generic;
+    using WixToolset.Data;
+    using WixToolset.Extensibility.Services;
+
+#pragma warning disable 1591 // TODO: add documentation
+    public interface IDecompileContext
+    {
+        IServiceProvider ServiceProvider { get; }
+
+        string DecompilePath { get; set; }
+
+        OutputType DecompileType { get; set; }
+
+        IReadOnlyCollection<IDecompilerExtension> Extensions { get; set; }
+
+        string ExtractFolder { get; set; }
+
+        string CabinetExtractFolder { get; set; }
+
+        /// <summary>
+        /// Optional gets or sets the base path for the File/@Source.
+        /// </summary>
+        /// <remarks>Default value is "SourceDir" to enable use of BindPaths.</remarks>
+        string BaseSourcePath { get; set; }
+
+        string IntermediateFolder { get; set; }
+
+        bool IsAdminImage { get; set; }
+
+        string OutputPath { get; set; }
+
+        /// <summary>
+        /// Gets or sets the option to suppress custom tables.
+        /// </summary>
+        bool SuppressCustomTables { get; set; }
+
+        /// <summary>
+        /// Gets or sets the option to suppress dropping empty tables.
+        /// </summary>
+        bool SuppressDroppingEmptyTables { get; set; }
+
+        bool SuppressExtractCabinets { get; set; }
+
+        /// <summary>
+        /// Gets or sets the option to suppress decompiling UI-related tables.
+        /// </summary>
+        bool SuppressUI { get; set; }
+
+        /// <summary>
+        /// Gets or sets whether the decompiler should use module logic on a product output.
+        /// </summary>
+        bool TreatProductAsModule { get; set; }
+    }
+}
diff --git a/src/api/wix/WixToolset.Extensibility/Data/IDecompileResult.cs b/src/api/wix/WixToolset.Extensibility/Data/IDecompileResult.cs
new file mode 100644
index 00000000..cffd0976
--- /dev/null
+++ b/src/api/wix/WixToolset.Extensibility/Data/IDecompileResult.cs
@@ -0,0 +1,18 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved. Licensed under the Microsoft Reciprocal License. See LICENSE.TXT file in the project root for full license information.
+
+namespace WixToolset.Extensibility.Data
+{
+    using System.Collections.Generic;
+    using System.Xml.Linq;
+    using WixToolset.Data;
+
+#pragma warning disable 1591 // TODO: add documentation
+    public interface IDecompileResult
+    {
+        XDocument Document { get; set; }
+
+        IReadOnlyCollection<string> ExtractedFilePaths { get; set; }
+
+        Platform? Platform { get; set; }
+    }
+}
diff --git a/src/api/wix/WixToolset.Extensibility/Data/IDelayedField.cs b/src/api/wix/WixToolset.Extensibility/Data/IDelayedField.cs
new file mode 100644
index 00000000..59a578a6
--- /dev/null
+++ b/src/api/wix/WixToolset.Extensibility/Data/IDelayedField.cs
@@ -0,0 +1,14 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved. Licensed under the Microsoft Reciprocal License. See LICENSE.TXT file in the project root for full license information.
+
+namespace WixToolset.Extensibility.Data
+{
+    using WixToolset.Data;
+
+#pragma warning disable 1591 // TODO: add documentation
+    public interface IDelayedField
+    {
+        IntermediateField Field { get; }
+
+        IntermediateSymbol Symbol { get; }
+    }
+}
diff --git a/src/api/wix/WixToolset.Extensibility/Data/IExpectedExtractFile.cs b/src/api/wix/WixToolset.Extensibility/Data/IExpectedExtractFile.cs
new file mode 100644
index 00000000..4bc8cd96
--- /dev/null
+++ b/src/api/wix/WixToolset.Extensibility/Data/IExpectedExtractFile.cs
@@ -0,0 +1,16 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved. Licensed under the Microsoft Reciprocal License. See LICENSE.TXT file in the project root for full license information.
+
+namespace WixToolset.Extensibility.Data
+{
+    using System;
+
+#pragma warning disable 1591 // TODO: add documentation
+    public interface IExpectedExtractFile
+    {
+        Uri Uri { get; set; }
+
+        string EmbeddedFileId { get; set; }
+
+        string OutputPath { get; set; }
+    }
+}
\ No newline at end of file
diff --git a/src/api/wix/WixToolset.Extensibility/Data/IFileFacade.cs b/src/api/wix/WixToolset.Extensibility/Data/IFileFacade.cs
new file mode 100644
index 00000000..fea00d4e
--- /dev/null
+++ b/src/api/wix/WixToolset.Extensibility/Data/IFileFacade.cs
@@ -0,0 +1,126 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved. Licensed under the Microsoft Reciprocal License. See LICENSE.TXT file in the project root for full license information.
+
+namespace WixToolset.Extensibility.Data
+{
+    using System.Collections.Generic;
+    using WixToolset.Data;
+    using WixToolset.Data.Symbols;
+    using WixToolset.Data.WindowsInstaller.Rows;
+
+    /// <summary>
+    /// Interface that provides a common facade over <c>FileSymbol</c> and <c>FileRow</c>.
+    /// </summary>
+    public interface IFileFacade
+    {
+        /// <summary>
+        /// Reference to assembly application for this file.
+        /// </summary>
+        string AssemblyApplicationFileRef { get; }
+
+        /// <summary>
+        /// Reference to assembly manifest for this file.
+        /// </summary>
+        string AssemblyManifestFileRef { get; }
+
+        /// <summary>
+        /// List of assembly name values in the file.
+        /// </summary>
+        List<MsiAssemblyNameSymbol> AssemblyNames { get; set; }
+
+        /// <summary>
+        /// Optionally indicates what sort of assembly the file is.
+        /// </summary>
+        AssemblyType? AssemblyType { get; }
+
+        /// <summary>
+        /// Component containing the file.
+        /// </summary>
+        string ComponentRef { get; }
+
+        /// <summary>
+        /// Indicates whether the file is compressed.
+        /// </summary>
+        bool Compressed { get; }
+
+        /// <summary>
+        /// Disk Id for the file.
+        /// </summary>
+        int DiskId { get; set; }
+
+        /// <summary>
+        /// Name of the file.
+        /// </summary>
+        string FileName { get; }
+
+        /// <summary>
+        /// Size of the file.
+        /// </summary>
+        int FileSize { get; set; }
+
+        /// <summary>
+        /// Indicates whether the file came from a merge module.
+        /// </summary>
+        bool FromModule { get; }
+
+        /// <summary>
+        /// Indicates whether the file came from a transform.
+        /// </summary>
+        bool FromTransform { get; }
+
+        /// <summary>
+        /// Hash symbol of the file.
+        /// </summary>
+        MsiFileHashSymbol Hash { get; set; }
+
+        /// <summary>
+        /// Underlying identifier of the file.
+        /// </summary>
+        Identifier Identifier { get; }
+
+        /// <summary>
+        /// Helper accessor for the Id of the Identifier.
+        /// </summary>
+        string Id { get; }
+
+        /// <summary>
+        /// Language of the file.
+        /// </summary>
+        string Language { get; set; }
+
+        /// <summary>
+        /// Optional patch group for the file.
+        /// </summary>
+        int? PatchGroup { get; }
+
+        /// <summary>
+        /// Sequence of the file.
+        /// </summary>
+        int Sequence { get; set; }
+
+        /// <summary>
+        /// Source line number that define the file.
+        /// </summary>
+        SourceLineNumber SourceLineNumber { get; }
+
+        /// <summary>
+        /// Source to the file.
+        /// </summary>
+        string SourcePath { get; }
+
+        /// <summary>
+        /// Indicates whether the file is to be uncompressed.
+        /// </summary>
+        bool Uncompressed { get; }
+
+        /// <summary>
+        /// Version of the file.
+        /// </summary>
+        string Version { get; set; }
+
+        /// <summary>
+        /// Gets the underlying <c>FileRow</c> if one is present.
+        /// </summary>
+        /// <returns><c>FileRow</c> if one is present, otherwise throws.</returns>
+        FileRow GetFileRow();
+    }
+}
diff --git a/src/api/wix/WixToolset.Extensibility/Data/IFileSystemContext.cs b/src/api/wix/WixToolset.Extensibility/Data/IFileSystemContext.cs
new file mode 100644
index 00000000..2e58059a
--- /dev/null
+++ b/src/api/wix/WixToolset.Extensibility/Data/IFileSystemContext.cs
@@ -0,0 +1,24 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved. Licensed under the Microsoft Reciprocal License. See LICENSE.TXT file in the project root for full license information.
+
+namespace WixToolset.Extensibility.Data
+{
+    using System;
+    using WixToolset.Data;
+    using WixToolset.Extensibility.Services;
+
+#pragma warning disable 1591 // TODO: add documentation
+    public interface IFileSystemContext
+    {
+        IServiceProvider ServiceProvider { get; }
+
+        string CabCachePath { get; set; }
+
+        string IntermediateFolder { get; set; }
+
+        Intermediate IntermediateRepresentation { get; set; }
+
+        string OutputPath { get; set; }
+
+        string OutputPdbPath { get; set; }
+    }
+}
diff --git a/src/api/wix/WixToolset.Extensibility/Data/IFileTransfer.cs b/src/api/wix/WixToolset.Extensibility/Data/IFileTransfer.cs
new file mode 100644
index 00000000..6f521536
--- /dev/null
+++ b/src/api/wix/WixToolset.Extensibility/Data/IFileTransfer.cs
@@ -0,0 +1,27 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved. Licensed under the Microsoft Reciprocal License. See LICENSE.TXT file in the project root for full license information.
+
+namespace WixToolset.Extensibility.Data
+{
+    using WixToolset.Data;
+
+    /// <summary>
+    /// Structure used for all file transfer information.
+    /// </summary>
+    public interface IFileTransfer
+    {
+        /// <summary>Destination path for file.</summary>
+        string Destination { get; set; }
+
+        /// <summary>Flag if file should be moved (optimal).</summary>
+        bool Move { get; set; }
+
+        /// <summary>Set during layout of media when the file transfer when the source and target resolve to the same path.</summary>
+        bool Redundant { get; set; }
+
+        /// <summary>Source path to file.</summary>
+        string Source { get; set; }
+
+        /// <summary>Optional source line numbers where this file transfer orginated.</summary>
+        SourceLineNumber SourceLineNumbers { get; set; }
+    }
+}
diff --git a/src/api/wix/WixToolset.Extensibility/Data/IIncludedFile.cs b/src/api/wix/WixToolset.Extensibility/Data/IIncludedFile.cs
new file mode 100644
index 00000000..e25c9f7e
--- /dev/null
+++ b/src/api/wix/WixToolset.Extensibility/Data/IIncludedFile.cs
@@ -0,0 +1,24 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved. Licensed under the Microsoft Reciprocal License. See LICENSE.TXT file in the project root for full license information.
+
+namespace WixToolset.Extensibility.Data
+{
+    using WixToolset.Data;
+
+    /// <summary>
+    /// Interface for an included file.
+    /// </summary>
+    public interface IIncludedFile
+    {
+        /// <summary>
+        /// Gets the full path of the included file.
+        /// </summary>
+        /// <value>The full path of the included file.</value>
+        string Path { get; set; }
+
+        /// <summary>
+        /// Gets the source line numbers.
+        /// </summary>
+        /// <value>The source line numbers.</value>
+        SourceLineNumber SourceLineNumbers { get; set; }
+    }
+}
diff --git a/src/api/wix/WixToolset.Extensibility/Data/IInscribeContext.cs b/src/api/wix/WixToolset.Extensibility/Data/IInscribeContext.cs
new file mode 100644
index 00000000..31c66aad
--- /dev/null
+++ b/src/api/wix/WixToolset.Extensibility/Data/IInscribeContext.cs
@@ -0,0 +1,21 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved. Licensed under the Microsoft Reciprocal License. See LICENSE.TXT file in the project root for full license information.
+
+namespace WixToolset.Extensibility.Data
+{
+    using System;
+    using WixToolset.Extensibility.Services;
+
+#pragma warning disable 1591 // TODO: add documentation
+    public interface IInscribeContext
+    {
+        IServiceProvider ServiceProvider { get; }
+
+        string InputFilePath { get; set; }
+
+        string IntermediateFolder { get; set; }
+
+        string OutputFile { get; set; }
+
+        string SignedEngineFile { get; set; }
+    }
+}
diff --git a/src/api/wix/WixToolset.Extensibility/Data/ILayoutContext.cs b/src/api/wix/WixToolset.Extensibility/Data/ILayoutContext.cs
new file mode 100644
index 00000000..b11b4d13
--- /dev/null
+++ b/src/api/wix/WixToolset.Extensibility/Data/ILayoutContext.cs
@@ -0,0 +1,64 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved. Licensed under the Microsoft Reciprocal License. See LICENSE.TXT file in the project root for full license information.
+
+namespace WixToolset.Extensibility.Data
+{
+    using System;
+    using System.Collections.Generic;
+    using System.Threading;
+
+    /// <summary>
+    /// Context for laying out files.
+    /// </summary>
+    public interface ILayoutContext
+    {
+        /// <summary>
+        /// Service provider.
+        /// </summary>
+        IServiceProvider ServiceProvider { get; }
+
+        /// <summary>
+        /// Extensions for use during layout.
+        /// </summary>
+        IReadOnlyCollection<ILayoutExtension> Extensions { get; set; }
+
+        /// <summary>
+        /// Set of tracked of files created during processing to be cleaned up.
+        /// </summary>
+        IReadOnlyCollection<ITrackedFile> TrackedFiles { get; set; }
+
+        /// <summary>
+        /// Set of files to transfer.
+        /// </summary>
+        IReadOnlyCollection<IFileTransfer> FileTransfers { get; set; }
+
+        /// <summary>
+        /// File to capture list of content files.
+        /// </summary>
+        string ContentsFile { get; set; }
+
+        /// <summary>
+        /// File to capture list of output files.
+        /// </summary>
+        string OutputsFile { get; set; }
+
+        /// <summary>
+        /// Intermediate folder.
+        /// </summary>
+        string IntermediateFolder { get; set; }
+
+        /// <summary>
+        /// List of built output files.
+        /// </summary>
+        string BuiltOutputsFile { get; set; }
+
+        /// <summary>
+        /// Reset ACLs on file transfers.
+        /// </summary>
+        bool ResetAcls { get; set; }
+
+        /// <summary>
+        /// Cancellation token.
+        /// </summary>
+        CancellationToken CancellationToken { get; set; }
+    }
+}
diff --git a/src/api/wix/WixToolset.Extensibility/Data/ILibraryContext.cs b/src/api/wix/WixToolset.Extensibility/Data/ILibraryContext.cs
new file mode 100644
index 00000000..208b6f73
--- /dev/null
+++ b/src/api/wix/WixToolset.Extensibility/Data/ILibraryContext.cs
@@ -0,0 +1,55 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved. Licensed under the Microsoft Reciprocal License. See LICENSE.TXT file in the project root for full license information.
+
+namespace WixToolset.Extensibility.Data
+{
+    using System;
+    using System.Collections.Generic;
+    using System.Threading;
+    using WixToolset.Data;
+
+    /// <summary>
+    /// Context provided during library creation operations.
+    /// </summary>
+    public interface ILibraryContext
+    {
+        /// <summary>
+        /// Service provider.
+        /// </summary>
+        IServiceProvider ServiceProvider { get; }
+
+        /// <summary>
+        /// Indicates whether files should be bound into the library.
+        /// </summary>
+        bool BindFiles { get; set; }
+
+        /// <summary>
+        /// Collection of bindpaths used to bind files.
+        /// </summary>
+        IReadOnlyCollection<IBindPath> BindPaths { get; set; }
+
+        /// <summary>
+        /// Collection of extensions used during creation of library.
+        /// </summary>
+        IReadOnlyCollection<ILibrarianExtension> Extensions { get; set; }
+
+        /// <summary>
+        /// Identifier of the library.
+        /// </summary>
+        string LibraryId { get; set; }
+
+        /// <summary>
+        /// Collection of localization files to use in the library.
+        /// </summary>
+        IReadOnlyCollection<Localization> Localizations { get; set; }
+
+        /// <summary>
+        /// Collection of intermediates to include in the library.
+        /// </summary>
+        IReadOnlyCollection<Intermediate> Intermediates { get; set; }
+
+        /// <summary>
+        /// Cancellation token.
+        /// </summary>
+        CancellationToken CancellationToken { get; set; }
+    }
+}
diff --git a/src/api/wix/WixToolset.Extensibility/Data/ILinkContext.cs b/src/api/wix/WixToolset.Extensibility/Data/ILinkContext.cs
new file mode 100644
index 00000000..d56866f7
--- /dev/null
+++ b/src/api/wix/WixToolset.Extensibility/Data/ILinkContext.cs
@@ -0,0 +1,50 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved. Licensed under the Microsoft Reciprocal License. See LICENSE.TXT file in the project root for full license information.
+
+namespace WixToolset.Extensibility.Data
+{
+    using System;
+    using System.Collections.Generic;
+    using System.Threading;
+    using WixToolset.Data;
+
+    /// <summary>
+    /// Context provided during linking.
+    /// </summary>
+    public interface ILinkContext
+    {
+        /// <summary>
+        /// Service provider.
+        /// </summary>
+        IServiceProvider ServiceProvider { get; }
+
+        /// <summary>
+        /// Collection of extensions to use during linking.
+        /// </summary>
+        IReadOnlyCollection<ILinkerExtension> Extensions { get; set; }
+
+        /// <summary>
+        /// Collection of extension data to use during linking.
+        /// </summary>
+        IReadOnlyCollection<IExtensionData> ExtensionData { get; set; }
+
+        /// <summary>
+        /// Expected output type.
+        /// </summary>
+        OutputType ExpectedOutputType { get; set; }
+
+        /// <summary>
+        /// Collection of intermediates to link.
+        /// </summary>
+        IReadOnlyCollection<Intermediate> Intermediates { get; set; }
+
+        /// <summary>
+        /// Symbol definition creator used to load extension data.
+        /// </summary>
+        ISymbolDefinitionCreator SymbolDefinitionCreator { get; set; }
+
+        /// <summary>
+        /// Cancellation token.
+        /// </summary>
+        CancellationToken CancellationToken { get; set; }
+    }
+}
diff --git a/src/api/wix/WixToolset.Extensibility/Data/IPreprocessContext.cs b/src/api/wix/WixToolset.Extensibility/Data/IPreprocessContext.cs
new file mode 100644
index 00000000..69057c33
--- /dev/null
+++ b/src/api/wix/WixToolset.Extensibility/Data/IPreprocessContext.cs
@@ -0,0 +1,56 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved. Licensed under the Microsoft Reciprocal License. See LICENSE.TXT file in the project root for full license information.
+
+namespace WixToolset.Extensibility.Data
+{
+    using System;
+    using System.Collections.Generic;
+    using System.Threading;
+    using WixToolset.Data;
+
+    /// <summary>
+    /// Preprocessor context.
+    /// </summary>
+    public interface IPreprocessContext
+    {
+        /// <summary>
+        /// Service provider.
+        /// </summary>
+        IServiceProvider ServiceProvider { get; }
+
+        /// <summary>
+        /// Collection of extensions to use during preprocessing.
+        /// </summary>
+        IReadOnlyCollection<IPreprocessorExtension> Extensions { get; set; }
+
+        /// <summary>
+        /// Collection of search paths to find include files.
+        /// </summary>
+        IReadOnlyCollection<string> IncludeSearchPaths { get; set; }
+
+        /// <summary>
+        /// Gets the platform which the compiler will use when defaulting 64-bit attributes and elements.
+        /// </summary>
+        /// <value>The platform which the compiler will use when defaulting 64-bit attributes and elements.</value>
+        Platform Platform { get; set; }
+
+        /// <summary>
+        /// Path to the source file being preprocessed.
+        /// </summary>
+        string SourcePath { get; set; }
+
+        /// <summary>
+        /// Collection of name/value pairs used as preprocessor variables.
+        /// </summary>
+        IDictionary<string, string> Variables { get; set; }
+
+        /// <summary>
+        /// Current source line number of the preprocessor.
+        /// </summary>
+        SourceLineNumber CurrentSourceLineNumber { get; set; }
+
+        /// <summary>
+        /// Cancellation token.
+        /// </summary>
+        CancellationToken CancellationToken { get; set; }
+    }
+}
diff --git a/src/api/wix/WixToolset.Extensibility/Data/IPreprocessResult.cs b/src/api/wix/WixToolset.Extensibility/Data/IPreprocessResult.cs
new file mode 100644
index 00000000..af224c1e
--- /dev/null
+++ b/src/api/wix/WixToolset.Extensibility/Data/IPreprocessResult.cs
@@ -0,0 +1,23 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved. Licensed under the Microsoft Reciprocal License. See LICENSE.TXT file in the project root for full license information.
+
+namespace WixToolset.Extensibility.Data
+{
+    using System.Collections.Generic;
+    using System.Xml.Linq;
+
+    /// <summary>
+    /// Result of preprocessing.
+    /// </summary>
+    public interface IPreprocessResult
+    {
+        /// <summary>
+        /// Document result of preprocessor.
+        /// </summary>
+        XDocument Document { get; set; }
+
+        /// <summary>
+        /// Collection of files included during preprocessing.
+        /// </summary>
+        IReadOnlyCollection<IIncludedFile> IncludedFiles { get; set; }
+    }
+}
diff --git a/src/api/wix/WixToolset.Extensibility/Data/IResolveContext.cs b/src/api/wix/WixToolset.Extensibility/Data/IResolveContext.cs
new file mode 100644
index 00000000..63159ccb
--- /dev/null
+++ b/src/api/wix/WixToolset.Extensibility/Data/IResolveContext.cs
@@ -0,0 +1,65 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved. Licensed under the Microsoft Reciprocal License. See LICENSE.TXT file in the project root for full license information.
+
+namespace WixToolset.Extensibility.Data
+{
+    using System;
+    using System.Collections.Generic;
+    using System.Threading;
+    using WixToolset.Data;
+
+    /// <summary>
+    /// Context for resolve.
+    /// </summary>
+    public interface IResolveContext
+    {
+        /// <summary>
+        /// Service provider.
+        /// </summary>
+        IServiceProvider ServiceProvider { get; }
+
+        /// <summary>
+        /// Bind paths used during resolution.
+        /// </summary>
+        IReadOnlyCollection<IBindPath> BindPaths { get; set; }
+
+        /// <summary>
+        /// Resolve extensions.
+        /// </summary>
+        IReadOnlyCollection<IResolverExtension> Extensions { get; set; }
+
+        /// <summary>
+        /// Extension data.
+        /// </summary>
+        IReadOnlyCollection<IExtensionData> ExtensionData { get; set; }
+
+        /// <summary>
+        /// List of cultures to filter the localizations.
+        /// </summary>
+        IReadOnlyCollection<string> FilterCultures { get; set; }
+
+        /// <summary>
+        /// Intermediate folder.
+        /// </summary>
+        string IntermediateFolder { get; set; }
+
+        /// <summary>
+        /// Intermediate to resolve.
+        /// </summary>
+        Intermediate IntermediateRepresentation { get; set; }
+
+        /// <summary>
+        /// Localizations used to resolve.
+        /// </summary>
+        IReadOnlyCollection<Localization> Localizations { get; set; }
+
+        /// <summary>
+        /// Indicates whether to allow localization and bind variables to remain unresolved.
+        /// </summary>
+        bool AllowUnresolvedVariables { get; set; }
+
+        /// <summary>
+        /// Cancellation token.
+        /// </summary>
+        CancellationToken CancellationToken { get; set; }
+    }
+}
diff --git a/src/api/wix/WixToolset.Extensibility/Data/IResolveFileResult.cs b/src/api/wix/WixToolset.Extensibility/Data/IResolveFileResult.cs
new file mode 100644
index 00000000..2f0df96c
--- /dev/null
+++ b/src/api/wix/WixToolset.Extensibility/Data/IResolveFileResult.cs
@@ -0,0 +1,22 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved. Licensed under the Microsoft Reciprocal License. See LICENSE.TXT file in the project root for full license information.
+
+namespace WixToolset.Extensibility.Data
+{
+    using System.Collections.Generic;
+
+    /// <summary>
+    /// Result of resolving a file.
+    /// </summary>
+    public interface IResolveFileResult
+    {
+        /// <summary>
+        /// Collection of paths checked to find file.
+        /// </summary>
+        IReadOnlyCollection<string> CheckedPaths { get; set; }
+
+        /// <summary>
+        /// Path to found file, if found.
+        /// </summary>
+        string Path { get; set; }
+    }
+}
diff --git a/src/api/wix/WixToolset.Extensibility/Data/IResolveResult.cs b/src/api/wix/WixToolset.Extensibility/Data/IResolveResult.cs
new file mode 100644
index 00000000..0c5e0ccf
--- /dev/null
+++ b/src/api/wix/WixToolset.Extensibility/Data/IResolveResult.cs
@@ -0,0 +1,43 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved. Licensed under the Microsoft Reciprocal License. See LICENSE.TXT file in the project root for full license information.
+
+namespace WixToolset.Extensibility.Data
+{
+    using System.Collections.Generic;
+    using WixToolset.Data;
+
+    /// <summary>
+    /// Result of resolving localization and bind variables.
+    /// </summary>
+    public interface IResolveResult
+    {
+        /// <summary>
+        /// Resolved codepage, if provided.
+        /// </summary>
+        int? Codepage { get; set; }
+
+        /// <summary>
+        /// Resolved summary information codepage, if provided.
+        /// </summary>
+        int? SummaryInformationCodepage { get; set; }
+
+        /// <summary>
+        /// Resolved package language, if provided.
+        /// </summary>
+        int? PackageLcid { get; set; }
+
+        /// <summary>
+        /// Fields still requiring resolution.
+        /// </summary>
+        IReadOnlyCollection<IDelayedField> DelayedFields { get; set; }
+
+        /// <summary>
+        /// Files to extract from embedded .wixlibs.
+        /// </summary>
+        IReadOnlyCollection<IExpectedExtractFile> ExpectedEmbeddedFiles { get; set; }
+
+        /// <summary>
+        /// Resolved intermediate.
+        /// </summary>
+        Intermediate IntermediateRepresentation { get; set; }
+    }
+}
diff --git a/src/api/wix/WixToolset.Extensibility/Data/IResolvedCabinet.cs b/src/api/wix/WixToolset.Extensibility/Data/IResolvedCabinet.cs
new file mode 100644
index 00000000..0c07d387
--- /dev/null
+++ b/src/api/wix/WixToolset.Extensibility/Data/IResolvedCabinet.cs
@@ -0,0 +1,12 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved. Licensed under the Microsoft Reciprocal License. See LICENSE.TXT file in the project root for full license information.
+
+namespace WixToolset.Extensibility.Data
+{
+#pragma warning disable 1591 // TODO: add documentation
+    public interface IResolvedCabinet
+    {
+        CabinetBuildOption BuildOption { get; set; }
+
+        string Path { get; set; }
+    }
+}
diff --git a/src/api/wix/WixToolset.Extensibility/Data/IResolvedDirectory.cs b/src/api/wix/WixToolset.Extensibility/Data/IResolvedDirectory.cs
new file mode 100644
index 00000000..59de6e78
--- /dev/null
+++ b/src/api/wix/WixToolset.Extensibility/Data/IResolvedDirectory.cs
@@ -0,0 +1,19 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved. Licensed under the Microsoft Reciprocal License. See LICENSE.TXT file in the project root for full license information.
+
+namespace WixToolset.Extensibility.Data
+{
+    /// <summary>
+    /// Used for resolved directory information.
+    /// </summary>
+    public interface IResolvedDirectory
+    {
+        /// <summary>The directory parent.</summary>
+        string DirectoryParent { get; set; }
+
+        /// <summary>The name of this directory.</summary>
+        string Name { get; set; }
+
+        /// <summary>The path of this directory.</summary>
+        string Path { get; set; }
+    }
+}
diff --git a/src/api/wix/WixToolset.Extensibility/Data/ITrackedFile.cs b/src/api/wix/WixToolset.Extensibility/Data/ITrackedFile.cs
new file mode 100644
index 00000000..df36bd2b
--- /dev/null
+++ b/src/api/wix/WixToolset.Extensibility/Data/ITrackedFile.cs
@@ -0,0 +1,32 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved. Licensed under the Microsoft Reciprocal License. See LICENSE.TXT file in the project root for full license information.
+
+namespace WixToolset.Extensibility.Data
+{
+    using WixToolset.Data;
+
+    /// <summary>
+    /// Interface used to track all files processed.
+    /// </summary>
+    public interface ITrackedFile
+    {
+        /// <summary>
+        /// Indicates whether the tracked file should be cleaned by the project.
+        /// </summary>
+        bool Clean { get; set; }
+
+        /// <summary>
+        /// Path to tracked file.
+        /// </summary>
+        string Path { get; set; }
+
+        /// <summary>
+        /// Optional source line numbers where the tracked file was created.
+        /// </summary>
+        SourceLineNumber SourceLineNumbers { get; set; }
+
+        /// <summary>
+        /// Type of tracked file.
+        /// </summary>
+        TrackedFileType Type { get; set; }
+    }
+}
diff --git a/src/api/wix/WixToolset.Extensibility/Data/IUnbindContext.cs b/src/api/wix/WixToolset.Extensibility/Data/IUnbindContext.cs
new file mode 100644
index 00000000..6427422f
--- /dev/null
+++ b/src/api/wix/WixToolset.Extensibility/Data/IUnbindContext.cs
@@ -0,0 +1,24 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved. Licensed under the Microsoft Reciprocal License. See LICENSE.TXT file in the project root for full license information.
+
+namespace WixToolset.Extensibility.Data
+{
+    using System;
+
+#pragma warning disable 1591 // TODO: add documentation
+    public interface IUnbindContext
+    {
+        IServiceProvider ServiceProvider { get; }
+
+        string ExportBasePath { get; set; }
+
+        string InputFilePath { get; set; }
+
+        string IntermediateFolder { get; set; }
+
+        bool IsAdminImage { get; set; }
+
+        bool SuppressDemodularization { get; set; }
+
+        bool SuppressExtractCabinets { get; set; }
+    }
+}
\ No newline at end of file
diff --git a/src/api/wix/WixToolset.Extensibility/Data/PossibleKeyPathType.cs b/src/api/wix/WixToolset.Extensibility/Data/PossibleKeyPathType.cs
new file mode 100644
index 00000000..08e927e4
--- /dev/null
+++ b/src/api/wix/WixToolset.Extensibility/Data/PossibleKeyPathType.cs
@@ -0,0 +1,40 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved. Licensed under the Microsoft Reciprocal License. See LICENSE.TXT file in the project root for full license information.
+
+namespace WixToolset.Extensibility.Data
+{
+    /// <summary>
+    /// Key path types.
+    /// </summary>
+    public enum PossibleKeyPathType
+    {
+        /// <summary>
+        /// Not a key path.
+        /// </summary>
+        None,
+
+        /// <summary>
+        /// File resource as a key path.
+        /// </summary>
+        File,
+
+        /// <summary>
+        /// Folder as a key path.
+        /// </summary>
+        Directory,
+
+        /// <summary>
+        /// ODBC data source as a key path.
+        /// </summary>
+        OdbcDataSource,
+
+        /// <summary>
+        /// A simple registry key acting as a key path.
+        /// </summary>
+        Registry,
+
+        /// <summary>
+        /// A registry key that contains a formatted property acting as a key path.
+        /// </summary>
+        RegistryFormatted
+    }
+}
diff --git a/src/api/wix/WixToolset.Extensibility/Data/TrackedFileType.cs b/src/api/wix/WixToolset.Extensibility/Data/TrackedFileType.cs
new file mode 100644
index 00000000..e7f53842
--- /dev/null
+++ b/src/api/wix/WixToolset.Extensibility/Data/TrackedFileType.cs
@@ -0,0 +1,33 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved. Licensed under the Microsoft Reciprocal License. See LICENSE.TXT file in the project root for full license information.
+
+namespace WixToolset.Extensibility.Data
+{
+    /// <summary>
+    /// Tracked file types.
+    /// </summary>
+    public enum TrackedFileType
+    {
+        /// <summary>
+        /// File tracked as input (like content included in an .msi).
+        /// </summary>
+        Input,
+
+        /// <summary>
+        /// Temporary file (like an .idt or any other temporary file).
+        /// These are to be deleted before the build completes.
+        /// </summary>
+        Temporary,
+
+        /// <summary>
+        /// Intermediate file (like a .cab in the cabcache).
+        /// These are left for subsequent builds.
+        /// </summary>
+        Intermediate,
+
+        /// <summary>
+        /// Final output (like a .msi, .cab or .wixpdb).
+        /// These are the whole point of the build process.
+        /// </summary>
+        Final,
+    }
+}
diff --git a/src/api/wix/WixToolset.Extensibility/DecompilerConstants.cs b/src/api/wix/WixToolset.Extensibility/DecompilerConstants.cs
new file mode 100644
index 00000000..22e8530d
--- /dev/null
+++ b/src/api/wix/WixToolset.Extensibility/DecompilerConstants.cs
@@ -0,0 +1,20 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved. Licensed under the Microsoft Reciprocal License. See LICENSE.TXT file in the project root for full license information.
+
+namespace WixToolset.Extensibility
+{
+    /// <summary>
+    /// Constants used by decompiler.
+    /// </summary>
+    public static class DecompilerConstants
+    {
+        /// <summary>
+        /// 
+        /// </summary>
+        public const char PrimaryKeyDelimiter = '/';
+
+        /// <summary>
+        /// 
+        /// </summary>
+        public const string PrimaryKeyDelimiterString = "/";
+    }
+}
diff --git a/src/api/wix/WixToolset.Extensibility/DecompilerExtension.cs b/src/api/wix/WixToolset.Extensibility/DecompilerExtension.cs
new file mode 100644
index 00000000..b492cf3a
--- /dev/null
+++ b/src/api/wix/WixToolset.Extensibility/DecompilerExtension.cs
@@ -0,0 +1,61 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved. Licensed under the Microsoft Reciprocal License. See LICENSE.TXT file in the project root for full license information.
+
+namespace WixToolset.Extensibility
+{
+    using WixToolset.Data;
+
+#if BRING_BACK_LATER
+    /// <summary>
+    /// Base class for creating a decompiler extension.
+    /// </summary>
+    public abstract class DecompilerExtension : IDecompilerExtension
+    {
+        /// <summary>
+        /// Gets or sets the decompiler core for the extension.
+        /// </summary>
+        /// <value>The decompiler core for the extension.</value>
+        public IDecompilerCore Core { get; set; }
+
+        /// <summary>
+        /// Gets the table definitions this extension decompiles.
+        /// </summary>
+        /// <value>Table definitions this extension decompiles.</value>
+        public virtual TableDefinitionCollection TableDefinitions { get; protected set; }
+
+        /// <summary>
+        /// Gets the library that this decompiler wants removed from the decomipiled output.
+        /// </summary>
+        /// <param name="tableDefinitions">The table definitions to use while loading the library.</param>
+        /// <returns>The library for this extension or null if there is no library to be removed.</returns>
+        public virtual Library GetLibraryToRemove(TableDefinitionCollection tableDefinitions)
+        {
+            return null;
+        }
+
+        /// <summary>
+        /// Called at the beginning of the decompilation of a database.
+        /// </summary>
+        /// <param name="tables">The collection of all tables.</param>
+        public virtual void Initialize(TableIndexedCollection tables)
+        {
+        }
+
+        /// <summary>
+        /// Decompiles an extension table.
+        /// </summary>
+        /// <param name="table">The table to decompile.</param>
+        public virtual void DecompileTable(Table table)
+        {
+            this.Core.UnexpectedTable(table);
+        }
+
+        /// <summary>
+        /// Finalize decompilation.
+        /// </summary>
+        /// <param name="tables">The collection of all tables.</param>
+        public virtual void Finish(TableIndexedCollection tables)
+        {
+        }
+    }
+#endif
+}
diff --git a/src/api/wix/WixToolset.Extensibility/ExtensionHelper.cs b/src/api/wix/WixToolset.Extensibility/ExtensionHelper.cs
new file mode 100644
index 00000000..6b938a65
--- /dev/null
+++ b/src/api/wix/WixToolset.Extensibility/ExtensionHelper.cs
@@ -0,0 +1,55 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved. Licensed under the Microsoft Reciprocal License. See LICENSE.TXT file in the project root for full license information.
+
+namespace WixToolset.Extensibility
+{
+    using System;
+    using System.Collections.Specialized;
+    using System.IO;
+    using System.Reflection;
+    using System.Xml;
+    using WixToolset.Data;
+    using WixToolset.Extensibility;
+
+#if BRING_BACK_LATER
+    /// <summary>
+    /// The main class for a WiX extension.
+    /// </summary>
+    public static class ExtensionHelper
+    {
+        /// <summary>
+        /// Help for loading a library from an embedded resource.
+        /// </summary>
+        /// <param name="assembly">The assembly containing the embedded resource.</param>
+        /// <param name="resourceName">The name of the embedded resource being requested.</param>
+        /// <param name="tableDefinitions">The table definitions to use while loading the library.</param>
+        /// <returns>The loaded library.</returns>
+        public static Library LoadLibraryHelper(Assembly assembly, string resourceName, TableDefinitionCollection tableDefinitions)
+        {
+            using (Stream resourceStream = assembly.GetManifestResourceStream(resourceName))
+            {
+                UriBuilder uriBuilder = new UriBuilder();
+                uriBuilder.Scheme = "embeddedresource";
+                uriBuilder.Path = assembly.Location;
+                uriBuilder.Fragment = resourceName;
+
+                return Library.Load(resourceStream, uriBuilder.Uri, tableDefinitions, false);
+            }
+        }
+
+        /// <summary>
+        /// Helper for loading table definitions from an embedded resource.
+        /// </summary>
+        /// <param name="assembly">The assembly containing the embedded resource.</param>
+        /// <param name="resourceName">The name of the embedded resource being requested.</param>
+        /// <returns>The loaded table definitions.</returns>
+        public static TableDefinitionCollection LoadTableDefinitionHelper(Assembly assembly, string resourceName)
+        {
+            using (Stream resourceStream = assembly.GetManifestResourceStream(resourceName))
+            using (XmlReader reader = XmlReader.Create(resourceStream))
+            {
+                return TableDefinitionCollection.Load(reader);
+            }
+        }
+    }
+#endif
+}
diff --git a/src/api/wix/WixToolset.Extensibility/IBackend.cs b/src/api/wix/WixToolset.Extensibility/IBackend.cs
new file mode 100644
index 00000000..9579c3ca
--- /dev/null
+++ b/src/api/wix/WixToolset.Extensibility/IBackend.cs
@@ -0,0 +1,19 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved. Licensed under the Microsoft Reciprocal License. See LICENSE.TXT file in the project root for full license information.
+
+namespace WixToolset.Extensibility
+{
+    using WixToolset.Data;
+    using WixToolset.Extensibility.Data;
+
+#pragma warning disable 1591 // TODO: add documentation
+    public interface IBackend
+    {
+        IBindResult Bind(IBindContext context);
+
+        IDecompileResult Decompile(IDecompileContext context);
+
+        Intermediate Unbind(IUnbindContext context);
+
+        bool Inscribe(IInscribeContext context);
+    }
+}
diff --git a/src/api/wix/WixToolset.Extensibility/IBackendFactory.cs b/src/api/wix/WixToolset.Extensibility/IBackendFactory.cs
new file mode 100644
index 00000000..99a6704f
--- /dev/null
+++ b/src/api/wix/WixToolset.Extensibility/IBackendFactory.cs
@@ -0,0 +1,10 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved. Licensed under the Microsoft Reciprocal License. See LICENSE.TXT file in the project root for full license information.
+
+namespace WixToolset.Extensibility
+{
+#pragma warning disable 1591 // TODO: add documentation
+    public interface IBackendFactory
+    {
+        bool TryCreateBackend(string outputType, string outputPath, out IBackend backend);
+    }
+}
diff --git a/src/api/wix/WixToolset.Extensibility/IBinderExtension.cs b/src/api/wix/WixToolset.Extensibility/IBinderExtension.cs
new file mode 100644
index 00000000..dba09845
--- /dev/null
+++ b/src/api/wix/WixToolset.Extensibility/IBinderExtension.cs
@@ -0,0 +1,22 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved. Licensed under the Microsoft Reciprocal License. See LICENSE.TXT file in the project root for full license information.
+
+namespace WixToolset.Extensibility
+{
+    using WixToolset.Extensibility.Data;
+
+    /// <summary>
+    /// Interface all binder extensions implement.
+    /// </summary>
+    public interface IBinderExtension
+    {
+        /// <summary>
+        /// Called before binding occurs.
+        /// </summary>
+        void PreBind(IBindContext context);
+
+        /// <summary>
+        /// Called after all binding occurs.
+        /// </summary>
+        void PostBind(IBindResult result);
+    }
+}
diff --git a/src/api/wix/WixToolset.Extensibility/IBurnBackendBinderExtension.cs b/src/api/wix/WixToolset.Extensibility/IBurnBackendBinderExtension.cs
new file mode 100644
index 00000000..1dd4d9b1
--- /dev/null
+++ b/src/api/wix/WixToolset.Extensibility/IBurnBackendBinderExtension.cs
@@ -0,0 +1,64 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved. Licensed under the Microsoft Reciprocal License. See LICENSE.TXT file in the project root for full license information.
+
+namespace WixToolset.Extensibility
+{
+    using WixToolset.Data;
+    using WixToolset.Extensibility.Data;
+
+    /// <summary>
+    /// Interface all Burn backend extensions implement.
+    /// </summary>
+    public interface IBurnBackendBinderExtension
+    {
+        /// <summary>
+        /// Called before binding occurs.
+        /// </summary>
+        void PreBackendBind(IBindContext context);
+
+        /// <summary>
+        /// Called to find a file related to another source in the authoring. For example, most often used
+        /// to find cabinets and uncompressed files for an MSI package.
+        /// </summary>
+        /// <param name="source">Path to the source package.</param>
+        /// <param name="relatedSource">Expected path to the related file.</param>
+        /// <param name="type">Type of related file, such as "File" or "Cabinet"</param>
+        /// <param name="sourceLineNumbers">Source line number of source package.</param>
+        /// <returns><c>IResolveFileResult</c> if the related file was found, or null for default handling.</returns>
+        IResolveFileResult ResolveRelatedFile(string source, string relatedSource, string type, SourceLineNumber sourceLineNumbers);
+
+        /// <summary>
+        /// Called right before the output is bound into its final format.
+        /// </summary>
+        /// <param name="section">The finalized intermediate section.</param>
+        void SymbolsFinalized(IntermediateSection section);
+
+        /// <summary>
+        /// Called to customize the DownloadUrl provided in source cde.
+        /// </summary>
+        /// <param name="url">The value from the source code. May not actually be a URL.</param>
+        /// <param name="fallbackUrl">The default URL if the extension does not return a value.</param>
+        /// <param name="packageId">Identifier of the package.</param>
+        /// <param name="payloadId">Identifier of the payload.</param>
+        /// <param name="fileName">Filename of the payload.</param>
+        /// <returns>Url to override, or null to use default value.</returns>
+        string ResolveUrl(string url, string fallbackUrl, string packageId, string payloadId, string fileName);
+
+        /// <summary>
+        /// Called for each extension symbol that hasn't been handled yet.
+        /// Use IBurnBackendHelper to add data.
+        /// </summary>
+        /// <param name="section">The linked section.</param>
+        /// <param name="symbol">The current symbol.</param>
+        /// <returns>
+        /// True if the extension handled the symbol, false otherwise.
+        /// The Burn backend will warn on all unhandled symbols.
+        /// </returns>
+        bool TryProcessSymbol(IntermediateSection section, IntermediateSymbol symbol);
+
+        /// <summary>
+        /// Called after output is bound into its final format.
+        /// </summary>
+        /// <param name="result"></param>
+        void PostBackendBind(IBindResult result);
+    }
+}
diff --git a/src/api/wix/WixToolset.Extensibility/ICompilerExtension.cs b/src/api/wix/WixToolset.Extensibility/ICompilerExtension.cs
new file mode 100644
index 00000000..55ef683a
--- /dev/null
+++ b/src/api/wix/WixToolset.Extensibility/ICompilerExtension.cs
@@ -0,0 +1,61 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved. Licensed under the Microsoft Reciprocal License. See LICENSE.TXT file in the project root for full license information.
+
+namespace WixToolset.Extensibility
+{
+    using System.Collections.Generic;
+    using System.Xml.Linq;
+    using WixToolset.Data;
+    using WixToolset.Extensibility.Data;
+
+    /// <summary>
+    /// Interface all compiler extensions implement.
+    /// </summary>
+    public interface ICompilerExtension
+    {
+        /// <summary>
+        /// Gets the schema namespace for this extension.
+        /// </summary>
+        /// <value>Schema namespace supported by this extension.</value>
+        XNamespace Namespace { get; }
+
+        /// <summary>
+        /// Called at the beginning of the compilation of a source file.
+        /// </summary>
+        void PreCompile(ICompileContext context);
+
+        /// <summary>
+        /// Processes an attribute for the Compiler.
+        /// </summary>
+        /// <param name="intermediate">Parent intermediate.</param>
+        /// <param name="section">Parent section.</param>
+        /// <param name="parentElement">Parent element of attribute.</param>
+        /// <param name="attribute">Attribute to process.</param>
+        /// <param name="context">Extra information about the context in which this element is being parsed.</param>
+        void ParseAttribute(Intermediate intermediate, IntermediateSection section, XElement parentElement, XAttribute attribute, IDictionary<string, string> context);
+
+        /// <summary>
+        /// Processes an element for the Compiler.
+        /// </summary>
+        /// <param name="intermediate">Parent intermediate.</param>
+        /// <param name="section">Parent section.</param>
+        /// <param name="parentElement">Parent element of element to process.</param>
+        /// <param name="element">Element to process.</param>
+        /// <param name="context">Extra information about the context in which this element is being parsed.</param>
+        void ParseElement(Intermediate intermediate, IntermediateSection section, XElement parentElement, XElement element, IDictionary<string, string> context);
+
+        /// <summary>
+        /// Processes an element for the Compiler, with the ability to supply a component keypath.
+        /// </summary>
+        /// <param name="intermediate">Parent intermediate.</param>
+        /// <param name="section">Parent section.</param>
+        /// <param name="parentElement">Parent element of element to process.</param>
+        /// <param name="element">Element to process.</param>
+        /// <param name="context">Extra information about the context in which this element is being parsed.</param>
+        IComponentKeyPath ParsePossibleKeyPathElement(Intermediate intermediate, IntermediateSection section, XElement parentElement, XElement element, IDictionary<string, string> context);
+
+        /// <summary>
+        /// Called at the end of the compilation of a source file.
+        /// </summary>
+        void PostCompile(Intermediate intermediate);
+    }
+}
diff --git a/src/api/wix/WixToolset.Extensibility/IDecompilerExtension.cs b/src/api/wix/WixToolset.Extensibility/IDecompilerExtension.cs
new file mode 100644
index 00000000..24ef3bff
--- /dev/null
+++ b/src/api/wix/WixToolset.Extensibility/IDecompilerExtension.cs
@@ -0,0 +1,22 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved. Licensed under the Microsoft Reciprocal License. See LICENSE.TXT file in the project root for full license information.
+
+namespace WixToolset.Extensibility
+{
+    using WixToolset.Extensibility.Data;
+
+    /// <summary>
+    /// Base class for creating a decompiler extension.
+    /// </summary>
+    public interface IDecompilerExtension
+    {
+        /// <summary>
+        /// Called before decompiling occurs.
+        /// </summary>
+        void PreDecompile(IDecompileContext context);
+
+        /// <summary>
+        /// Called after all decompiling occurs.
+        /// </summary>
+        void PostDecompile(IDecompileResult result);
+    }
+}
diff --git a/src/api/wix/WixToolset.Extensibility/IExtensionCommandLine.cs b/src/api/wix/WixToolset.Extensibility/IExtensionCommandLine.cs
new file mode 100644
index 00000000..f7b19955
--- /dev/null
+++ b/src/api/wix/WixToolset.Extensibility/IExtensionCommandLine.cs
@@ -0,0 +1,48 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved. Licensed under the Microsoft Reciprocal License. See LICENSE.TXT file in the project root for full license information.
+
+namespace WixToolset.Extensibility
+{
+    using System.Collections.Generic;
+    using WixToolset.Extensibility.Data;
+    using WixToolset.Extensibility.Services;
+
+    /// <summary>
+    /// Interface extensions implement to be able to parse the command-line.
+    /// </summary>
+    public interface IExtensionCommandLine
+    {
+        /// <summary>
+        /// Gets the supported command line types for this extension.
+        /// </summary>
+        /// <value>The supported command line types for this extension.</value>
+        IReadOnlyCollection<ExtensionCommandLineSwitch> CommandLineSwitches { get; }
+
+        /// <summary>
+        /// Called before the command-line is parsed.
+        /// </summary>
+        /// <param name="context">Information about the command-line to be parsed.</param>
+        void PreParse(ICommandLineContext context);
+
+        /// <summary>
+        /// Gives the extension an opportunity pass a command-line argument for another command.
+        /// </summary>
+        /// <param name="parser">Parser to help parse the argument and additional arguments.</param>
+        /// <param name="argument">Argument to parse.</param>
+        /// <returns>True if the argument is recognized; otherwise false to allow another extension to process it.</returns>
+        bool TryParseArgument(ICommandLineParser parser, string argument);
+
+        /// <summary>
+        /// Gives the extension an opportunity to provide a command.
+        /// </summary>
+        /// <param name="parser">Parser to help parse the argument and additional arguments.</param>
+        /// <param name="argument">Argument to parse.</param>
+        /// <param name="command"></param>
+        /// <returns>True if the argument is recognized as a command; otherwise false to allow another extension to process it.</returns>
+        bool TryParseCommand(ICommandLineParser parser, string argument, out ICommandLineCommand command);
+
+        /// <summary>
+        /// Called after the command-line is parsed.
+        /// </summary>
+        void PostParse();
+    }
+}
diff --git a/src/api/wix/WixToolset.Extensibility/IExtensionData.cs b/src/api/wix/WixToolset.Extensibility/IExtensionData.cs
new file mode 100644
index 00000000..823e2beb
--- /dev/null
+++ b/src/api/wix/WixToolset.Extensibility/IExtensionData.cs
@@ -0,0 +1,33 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved. Licensed under the Microsoft Reciprocal License. See LICENSE.TXT file in the project root for full license information.
+
+namespace WixToolset.Extensibility
+{
+    using WixToolset.Data;
+
+    /// <summary>
+    /// Interface extensions implement to provide data.
+    /// </summary>
+    public interface IExtensionData
+    {
+        /// <summary>
+        /// Gets the optional default culture.
+        /// </summary>
+        /// <value>The optional default culture.</value>
+        string DefaultCulture { get; }
+
+        /// <summary>
+        ///
+        /// </summary>
+        /// <param name="name"></param>
+        /// <param name="symbolDefinition"></param>
+        /// <returns>True </returns>
+        bool TryGetSymbolDefinitionByName(string name, out IntermediateSymbolDefinition symbolDefinition);
+
+        /// <summary>
+        /// Gets the library associated with this extension.
+        /// </summary>
+        /// <param name="symbolDefinitions">The symbol definitions to use while loading the library.</param>
+        /// <returns>The library for this extension or null if there is no library.</returns>
+        Intermediate GetLibrary(ISymbolDefinitionCreator symbolDefinitions);
+    }
+}
diff --git a/src/api/wix/WixToolset.Extensibility/IExtensionFactory.cs b/src/api/wix/WixToolset.Extensibility/IExtensionFactory.cs
new file mode 100644
index 00000000..f86fdde0
--- /dev/null
+++ b/src/api/wix/WixToolset.Extensibility/IExtensionFactory.cs
@@ -0,0 +1,20 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved. Licensed under the Microsoft Reciprocal License. See LICENSE.TXT file in the project root for full license information.
+
+namespace WixToolset.Extensibility
+{
+    using System;
+
+    /// <summary>
+    /// Implementations may request an IWixToolsetCoreServiceProvider at instantiation by having a single parameter constructor for it.
+    /// </summary>
+    public interface IExtensionFactory
+    {
+        /// <summary>
+        /// Request to create an extension of the specified type.
+        /// </summary>
+        /// <param name="extensionType">Extension type to create.</param>
+        /// <param name="extension">Extension created.</param>
+        /// <returns>True if extension was created; otherwise false.</returns>
+        bool TryCreateExtension(Type extensionType, out object extension);
+    }
+}
diff --git a/src/api/wix/WixToolset.Extensibility/IFileSystemExtension.cs b/src/api/wix/WixToolset.Extensibility/IFileSystemExtension.cs
new file mode 100644
index 00000000..9807e8b9
--- /dev/null
+++ b/src/api/wix/WixToolset.Extensibility/IFileSystemExtension.cs
@@ -0,0 +1,17 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved. Licensed under the Microsoft Reciprocal License. See LICENSE.TXT file in the project root for full license information.
+
+namespace WixToolset.Extensibility
+{
+    using WixToolset.Extensibility.Data;
+
+    /// <summary>
+    /// Interface all file system extensions implement.
+    /// </summary>
+    public interface IFileSystemExtension
+    {
+#pragma warning disable 1591 // TODO: add documentation
+        void Initialize(IFileSystemContext context);
+
+        bool? CompareFiles(string targetFile, string updatedFile);
+    }
+}
diff --git a/src/api/wix/WixToolset.Extensibility/IInspectorCore.cs b/src/api/wix/WixToolset.Extensibility/IInspectorCore.cs
new file mode 100644
index 00000000..9420ea05
--- /dev/null
+++ b/src/api/wix/WixToolset.Extensibility/IInspectorCore.cs
@@ -0,0 +1,15 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved. Licensed under the Microsoft Reciprocal License. See LICENSE.TXT file in the project root for full license information.
+
+namespace WixToolset.Extensibility
+{
+    /// <summary>
+    /// Core facilities for inspector extensions.
+    /// </summary>
+    public interface IInspectorCore
+    {
+        /// <summary>
+        /// Gets whether an error occured.
+        /// </summary>
+        bool EncounteredError { get; }
+    }
+}
diff --git a/src/api/wix/WixToolset.Extensibility/IInspectorExtension.cs b/src/api/wix/WixToolset.Extensibility/IInspectorExtension.cs
new file mode 100644
index 00000000..7c488a89
--- /dev/null
+++ b/src/api/wix/WixToolset.Extensibility/IInspectorExtension.cs
@@ -0,0 +1,60 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved. Licensed under the Microsoft Reciprocal License. See LICENSE.TXT file in the project root for full license information.
+
+namespace WixToolset.Extensibility
+{
+    using System;
+    using System.IO;
+    using WixToolset.Data;
+
+    /// <summary>
+    /// Interface for inspector extensions.
+    /// </summary>
+    /// <remarks>
+    /// The inspector methods are stateless, but extensions are loaded once. If you want to maintain state, you should check
+    /// if your data is loaded for each method and, if not, load it.
+    /// </remarks>
+    public interface IInspectorExtension
+    {
+        /// <summary>
+        /// Gets or sets the <see cref="IInspectorCore"/> for inspector extensions to use.
+        /// </summary>
+        IInspectorCore Core { get; set; }
+
+        /// <summary>
+        /// Inspect the source before preprocessing.
+        /// </summary>
+        /// <param name="source">The source to preprocess.</param>
+        void InspectSource(Stream source);
+
+        /// <summary>
+        /// Inspect the compiled output.
+        /// </summary>
+        /// <param name="intermediate">The compiled output.</param>
+        void InspectIntermediate(Intermediate intermediate);
+
+#if REWRITE
+        /// <summary>
+        /// Inspect the output.
+        /// </summary>
+        /// <param name="output">The output. May be called after linking or binding.</param>
+        /// <remarks>
+        /// To inspect a patch's filtered transforms, enumerate <see cref="Output.SubStorages"/>.
+        /// Transforms where the <see cref="SubStorage.Name"/> begins with "#" are
+        /// called patch transforms and instruct Windows Installer how to apply the
+        /// authored transforms - those that do not begin with "#". The authored
+        /// transforms are the primary transforms you'll typically want to inspect
+        /// and contain your changes to target products.
+        /// </remarks>
+#endif
+        /// <summary />
+        void InspectOutput(Intermediate output);
+
+        /// <summary>
+        /// Inspect the final output after binding.
+        /// </summary>
+        /// <param name="filePath">The file path to the final bound output.</param>
+        /// <param name="pdb">The <see cref="Intermediate"/> that contains source line numbers
+        /// for the database and all rows.</param>
+        void InspectDatabase(string filePath, Intermediate pdb);
+    }
+}
diff --git a/src/api/wix/WixToolset.Extensibility/ILayoutExtension.cs b/src/api/wix/WixToolset.Extensibility/ILayoutExtension.cs
new file mode 100644
index 00000000..ecd7d8f1
--- /dev/null
+++ b/src/api/wix/WixToolset.Extensibility/ILayoutExtension.cs
@@ -0,0 +1,28 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved. Licensed under the Microsoft Reciprocal License. See LICENSE.TXT file in the project root for full license information.
+
+namespace WixToolset.Extensibility
+{
+    using WixToolset.Extensibility.Data;
+
+    /// <summary>
+    /// Interface all layout extensions implement.
+    /// </summary>
+    public interface ILayoutExtension
+    {
+        /// <summary>
+        /// Called before layout occurs.
+        /// </summary>
+        void PreLayout(ILayoutContext context);
+
+#pragma warning disable 1591 // TODO: add documentation
+        bool CopyFile(string source, string destination);
+
+        bool MoveFile(string source, string destination);
+#pragma warning restore 1591
+
+        /// <summary>
+        /// Called after all layout occurs.
+        /// </summary>
+        void PostLayout();
+    }
+}
diff --git a/src/api/wix/WixToolset.Extensibility/ILibrarianExtension.cs b/src/api/wix/WixToolset.Extensibility/ILibrarianExtension.cs
new file mode 100644
index 00000000..d9b04cd2
--- /dev/null
+++ b/src/api/wix/WixToolset.Extensibility/ILibrarianExtension.cs
@@ -0,0 +1,17 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved. Licensed under the Microsoft Reciprocal License. See LICENSE.TXT file in the project root for full license information.
+
+namespace WixToolset.Extensibility
+{
+    using WixToolset.Data;
+    using WixToolset.Extensibility.Data;
+
+#pragma warning disable 1591 // TODO: add documentation
+    public interface ILibrarianExtension
+    {
+        void PreCombine(ILibraryContext context);
+
+        IResolveFileResult ResolveFile(SourceLineNumber sourceLineNumber, IntermediateSymbolDefinition symbolDefinition, string path);
+
+        void PostCombine(Intermediate library);
+    }
+}
diff --git a/src/api/wix/WixToolset.Extensibility/ILinkerExtension.cs b/src/api/wix/WixToolset.Extensibility/ILinkerExtension.cs
new file mode 100644
index 00000000..febca1df
--- /dev/null
+++ b/src/api/wix/WixToolset.Extensibility/ILinkerExtension.cs
@@ -0,0 +1,23 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved. Licensed under the Microsoft Reciprocal License. See LICENSE.TXT file in the project root for full license information.
+
+namespace WixToolset.Extensibility
+{
+    using WixToolset.Data;
+    using WixToolset.Extensibility.Data;
+
+    /// <summary>
+    /// Interface all binder extensions implement.
+    /// </summary>
+    public interface ILinkerExtension
+    {
+        /// <summary>
+        /// Called before linking occurs.
+        /// </summary>
+        void PreLink(ILinkContext context);
+
+        /// <summary>
+        /// Called after all linking occurs.
+        /// </summary>
+        void PostLink(Intermediate intermediate);
+    }
+}
diff --git a/src/api/wix/WixToolset.Extensibility/IMessageListener.cs b/src/api/wix/WixToolset.Extensibility/IMessageListener.cs
new file mode 100644
index 00000000..a04e9c98
--- /dev/null
+++ b/src/api/wix/WixToolset.Extensibility/IMessageListener.cs
@@ -0,0 +1,34 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved. Licensed under the Microsoft Reciprocal License. See LICENSE.TXT file in the project root for full license information.
+
+namespace WixToolset.Extensibility
+{
+    using WixToolset.Data;
+    using WixToolset.Extensibility.Services;
+
+    /// <summary>
+    /// Message listener.
+    /// </summary>
+    public interface IMessageListener
+    {
+        /// <summary>
+        /// Calculate a new level for a message.
+        /// </summary>
+        /// <param name="messaging">Messaging object.</param>
+        /// <param name="message">Message to evaluate.</param>
+        /// <param name="defaultMessageLevel">Current message level.</param>
+        /// <returns></returns>
+        MessageLevel CalculateMessageLevel(IMessaging messaging, Message message, MessageLevel defaultMessageLevel);
+
+        /// <summary>
+        /// Writes a message.
+        /// </summary>
+        /// <param name="message">Message to write.</param>
+        void Write(Message message);
+
+        /// <summary>
+        /// Writes a string message.
+        /// </summary>
+        /// <param name="message">String message to write.</param>
+        void Write(string message);
+    }
+}
diff --git a/src/api/wix/WixToolset.Extensibility/IPreprocessorExtension.cs b/src/api/wix/WixToolset.Extensibility/IPreprocessorExtension.cs
new file mode 100644
index 00000000..919ff1ae
--- /dev/null
+++ b/src/api/wix/WixToolset.Extensibility/IPreprocessorExtension.cs
@@ -0,0 +1,57 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved. Licensed under the Microsoft Reciprocal License. See LICENSE.TXT file in the project root for full license information.
+
+namespace WixToolset.Extensibility
+{
+    using System.Xml.Linq;
+    using WixToolset.Extensibility.Data;
+
+    /// <summary>
+    /// Interface for extending the WiX toolset preprocessor.
+    /// </summary>
+    public interface IPreprocessorExtension
+    {
+        /// <summary>
+        /// Gets the variable prefixes for the extension.
+        /// </summary>
+        /// <value>The variable prefixes for the extension.</value>
+        string[] Prefixes { get; }
+
+        /// <summary>
+        /// Called at the beginning of the preprocessing of a source file.
+        /// </summary>
+        void PrePreprocess(IPreprocessContext context);
+
+        /// <summary>
+        /// Gets the value of a variable whose prefix matches the extension.
+        /// </summary>
+        /// <param name="prefix">The prefix of the variable to be processed by the extension.</param>
+        /// <param name="name">The name of the variable.</param>
+        /// <returns>The value of the variable or null if the variable is undefined.</returns>
+        string GetVariableValue(string prefix, string name);
+
+        /// <summary>
+        /// Evaluates a function defined in the extension.
+        /// </summary>
+        /// <param name="prefix">The prefix of the function to be processed by the extension.</param>
+        /// <param name="function">The name of the function.</param>
+        /// <param name="args">The list of arguments.</param>
+        /// <returns>The value of the function or null if the function is not defined.</returns>
+        string EvaluateFunction(string prefix, string function, string[] args);
+
+        /// <summary>
+        /// Processes a pragma defined in the extension.
+        /// </summary>
+        /// <param name="prefix">The prefix of the pragma to be processed by the extension.</param>
+        /// <param name="pragma">The name of the pragma.</param>
+        /// <param name="args">The pragma's arguments.</param>
+        /// <param name="parent">The parent node of the pragma.</param>
+        /// <returns>false if the pragma is not defined.</returns>
+        /// <comments>Don't return false for any condition except for unrecognized pragmas. Use Core.OnMessage for errors, warnings and messages.</comments>
+        bool ProcessPragma(string prefix, string pragma, string args, XContainer parent);
+
+        /// <summary>
+        /// Called at the end of the preprocessing of a source file.
+        /// </summary>
+        void PostPreprocess(IPreprocessResult result);
+    }
+}
diff --git a/src/api/wix/WixToolset.Extensibility/IResolverExtension.cs b/src/api/wix/WixToolset.Extensibility/IResolverExtension.cs
new file mode 100644
index 00000000..f77581a0
--- /dev/null
+++ b/src/api/wix/WixToolset.Extensibility/IResolverExtension.cs
@@ -0,0 +1,28 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved. Licensed under the Microsoft Reciprocal License. See LICENSE.TXT file in the project root for full license information.
+
+namespace WixToolset.Extensibility
+{
+    using WixToolset.Data;
+    using WixToolset.Extensibility.Data;
+
+    /// <summary>
+    /// Interface all resolver extensions implement.
+    /// </summary>
+    public interface IResolverExtension
+    {
+        /// <summary>
+        /// Called before resolving occurs.
+        /// </summary>
+        void PreResolve(IResolveContext context);
+
+        /// <summary>
+        /// Called to attempt to resolve source to a file.
+        /// </summary>
+        IResolveFileResult ResolveFile(string source, IntermediateSymbolDefinition symbolDefinition, SourceLineNumber sourceLineNumbers, BindStage bindStage);
+
+        /// <summary>
+        /// Called after all resolving occurs.
+        /// </summary>
+        void PostResolve(IResolveResult result);
+    }
+}
diff --git a/src/api/wix/WixToolset.Extensibility/IUnbinderExtension.cs b/src/api/wix/WixToolset.Extensibility/IUnbinderExtension.cs
new file mode 100644
index 00000000..0e9a2504
--- /dev/null
+++ b/src/api/wix/WixToolset.Extensibility/IUnbinderExtension.cs
@@ -0,0 +1,18 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved. Licensed under the Microsoft Reciprocal License. See LICENSE.TXT file in the project root for full license information.
+
+namespace WixToolset.Extensibility
+{
+    using System;
+    using WixToolset.Data;
+
+    /// <summary>
+    /// Base class for creating an unbinder extension.
+    /// </summary>
+    public interface IUnbinderExtension
+    {
+        /// <summary>
+        /// Called during the generation of sectionIds for an admin image.
+        /// </summary>
+        void GenerateSectionIds(Intermediate output);
+    }
+}
diff --git a/src/api/wix/WixToolset.Extensibility/IWindowsInstallerBackendBinderExtension.cs b/src/api/wix/WixToolset.Extensibility/IWindowsInstallerBackendBinderExtension.cs
new file mode 100644
index 00000000..067745c2
--- /dev/null
+++ b/src/api/wix/WixToolset.Extensibility/IWindowsInstallerBackendBinderExtension.cs
@@ -0,0 +1,65 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved. Licensed under the Microsoft Reciprocal License. See LICENSE.TXT file in the project root for full license information.
+
+namespace WixToolset.Extensibility
+{
+    using System.Collections.Generic;
+    using WixToolset.Data;
+    using WixToolset.Data.Symbols;
+    using WixToolset.Data.WindowsInstaller;
+    using WixToolset.Extensibility.Data;
+
+    /// <summary>
+    /// Interface all binder extensions implement.
+    /// </summary>
+    public interface IWindowsInstallerBackendBinderExtension
+    {
+        /// <summary>
+        /// Table definitions provided by the extension.
+        /// </summary>
+        IReadOnlyCollection<TableDefinition> TableDefinitions { get; }
+
+        /// <summary>
+        /// Called before binding occurs.
+        /// </summary>
+        void PreBackendBind(IBindContext context);
+
+        /// <summary>
+        /// Extension can process the intermediate before the Windows Installer data is created.
+        /// </summary>
+        /// <param name="section">The finalized intermediate section.</param>
+        void SymbolsFinalized(IntermediateSection section);
+
+        /// <summary>
+        /// Finds an existing cabinet that contains the provided files.
+        /// </summary>
+        /// <param name="cabinetPath">Path to the cabinet.</param>
+        /// <param name="files">Files contained in the cabinet.</param>
+        /// <returns>Resolved cabinet options or null if the cabinet could not be found.</returns>
+        IResolvedCabinet ResolveCabinet(string cabinetPath, IEnumerable<IBindFileWithPath> files);
+
+        /// <summary>
+        /// Override layout location for a media.
+        /// </summary>
+        /// <param name="mediaSymbol">Media symbol.</param>
+        /// <param name="mediaLayoutDirectory">Default media specific layout directory.</param>
+        /// <param name="layoutDirectory">Default overall layout directory.</param>
+        /// <returns>Layout location or null to use the default processing.</returns>
+        string ResolveMedia(MediaSymbol mediaSymbol, string mediaLayoutDirectory, string layoutDirectory);
+
+        /// <summary>
+        /// Called for each extension symbol that hasn't been handled yet.
+        /// </summary>
+        /// <param name="section">The linked section.</param>
+        /// <param name="symbol">The current symbol.</param>
+        /// <param name="data">Windows Installer data </param>
+        /// <param name="tableDefinitions">Collection of table definitions available for the output.</param>
+        /// <returns>True if the symbol was handled, or false if not.</returns>
+        bool TryProcessSymbol(IntermediateSection section, IntermediateSymbol symbol, WindowsInstallerData data, TableDefinitionCollection tableDefinitions);
+
+        /// <summary>
+        /// Called after all output changes occur and right before the output is bound into its final format.
+        /// </summary>
+        /// <param name="result">Bind result to process.</param>
+        void PostBackendBind(IBindResult result);
+    }
+}
diff --git a/src/api/wix/WixToolset.Extensibility/IWindowsInstallerBackendDecompilerExtension.cs b/src/api/wix/WixToolset.Extensibility/IWindowsInstallerBackendDecompilerExtension.cs
new file mode 100644
index 00000000..a56b63c3
--- /dev/null
+++ b/src/api/wix/WixToolset.Extensibility/IWindowsInstallerBackendDecompilerExtension.cs
@@ -0,0 +1,26 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved. Licensed under the Microsoft Reciprocal License. See LICENSE.TXT file in the project root for full license information.
+
+namespace WixToolset.Extensibility
+{
+    using WixToolset.Data;
+    using WixToolset.Data.WindowsInstaller;
+    using WixToolset.Extensibility.Data;
+
+    /// <summary>
+    /// Interface all binder extensions implement.
+    /// </summary>
+    public interface IWindowsInstallerBackendDecompilerExtension
+    {
+        /// <summary>
+        /// Called before decompiling occurs.
+        /// </summary>
+        void PreBackendDecompile(IDecompileContext context);
+
+        // TODO: Redesign this interface to be useful.
+
+        /// <summary>
+        /// Called after all output changes occur and right before the output is bound into its final format.
+        /// </summary>
+        void PostBackendDecompile(IDecompileResult result);
+    }
+}
diff --git a/src/api/wix/WixToolset.Extensibility/InspectorExtension.cs b/src/api/wix/WixToolset.Extensibility/InspectorExtension.cs
new file mode 100644
index 00000000..49c3f9de
--- /dev/null
+++ b/src/api/wix/WixToolset.Extensibility/InspectorExtension.cs
@@ -0,0 +1,63 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved. Licensed under the Microsoft Reciprocal License. See LICENSE.TXT file in the project root for full license information.
+
+namespace WixToolset.Extensibility
+{
+    using System;
+    using System.IO;
+    using WixToolset.Data;
+
+#if BRING_THIS_BACK
+    /// <summary>
+    /// Opitonal base class for inspector extensions.
+    /// </summary>
+    public class InspectorExtension : IInspectorExtension
+    {
+        /// <summary>
+        /// Gets the <see cref="InspectorCore"/> for inspector extensions to use.
+        /// </summary>
+        public IInspectorCore Core { get; set; }
+
+        /// <summary>
+        /// Inspect the source before preprocessing.
+        /// </summary>
+        /// <param name="source">The source to preprocess.</param>
+        public virtual void InspectSource(Stream source)
+        {
+        }
+
+        /// <summary>
+        /// Inspect the compiled output.
+        /// </summary>
+        /// <param name="intermediate">The compiled output.</param>
+        public virtual void InspectIntermediate(Intermediate intermediate)
+        {
+        }
+
+        /// <summary>
+        /// Inspect the output.
+        /// </summary>
+        /// <param name="output">The output. May be called after linking or binding.</param>
+        /// <remarks>
+        /// To inspect a patch's filtered transforms, enumerate <see cref="Output.SubStorages"/>.
+        /// Transforms where the <see cref="SubStorage.Name"/> begins with "#" are
+        /// called patch transforms and instruct Windows Installer how to apply the
+        /// authored transforms - those that do not begin with "#". The authored
+        /// transforms are the primary transforms you'll typically want to inspect
+        /// and contain your changes to target products.
+        /// </remarks>
+        public virtual void InspectOutput(Output output)
+        {
+        }
+
+        /// <summary>
+        /// Inspect the final output after binding.
+        /// </summary>
+        /// <param name="filePath">The file path to the final bound output.</param>
+        /// <param name="pdb">The <see cref="Pdb"/> that contains source line numbers
+        /// for the database and all rows.</param>
+        public virtual void InspectDatabase(string filePath, Pdb pdb)
+        {
+        }
+    }
+#endif
+}
diff --git a/src/api/wix/WixToolset.Extensibility/Services/IBackendHelper.cs b/src/api/wix/WixToolset.Extensibility/Services/IBackendHelper.cs
new file mode 100644
index 00000000..5c4d9a68
--- /dev/null
+++ b/src/api/wix/WixToolset.Extensibility/Services/IBackendHelper.cs
@@ -0,0 +1,183 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved. Licensed under the Microsoft Reciprocal License. See LICENSE.TXT file in the project root for full license information.
+
+namespace WixToolset.Extensibility.Services
+{
+    using System;
+    using System.Collections.Generic;
+    using WixToolset.Data;
+    using WixToolset.Data.Symbols;
+    using WixToolset.Data.WindowsInstaller.Rows;
+    using WixToolset.Extensibility.Data;
+
+    /// <summary>
+    /// Interface provided to help backend extensions.
+    /// </summary>
+    public interface IBackendHelper
+    {
+        /// <summary>
+        /// Creates a file facade from a <c>FileSymbol</c> and possible <c>AssemblySymbol</c>.
+        /// </summary>
+        /// <param name="file"><c>FileSymbol</c> backing the facade.</param>
+        /// <param name="assembly"><c>AssemblySymbol</c> backing the facade.</param>
+        /// <returns></returns>
+        IFileFacade CreateFileFacade(FileSymbol file, AssemblySymbol assembly);
+
+        /// <summary>
+        /// Creates a file facade from a File row.
+        /// </summary>
+        /// <param name="fileRow"><c>FileRow</c> </param>
+        /// <returns>New <c>IFileFacade</c>.</returns>
+        IFileFacade CreateFileFacade(FileRow fileRow);
+
+        /// <summary>
+        /// Creates a file facade from a Merge Module's File symbol.
+        /// </summary>
+        /// <param name="fileSymbol"><c>FileSymbol</c> created from a Merge Module.</param>
+        /// <returns>New <c>IFileFacade</c>.</returns>
+        IFileFacade CreateFileFacadeFromMergeModule(FileSymbol fileSymbol);
+
+        /// <summary>
+        /// Creates a file transfer and marks it redundant if the source and destination are identical.
+        /// </summary>
+        /// <param name="source">Source for the file transfer.</param>
+        /// <param name="destination">Destination for the file transfer.</param>
+        /// <param name="move">Indicates whether to move or copy the source file.</param>
+        /// <param name="sourceLineNumbers">Optional source line numbers that requested the file transfer.</param>
+        IFileTransfer CreateFileTransfer(string source, string destination, bool move, SourceLineNumber sourceLineNumbers = null);
+
+        /// <summary>
+        /// Creates a MSI compatible GUID.
+        /// </summary>
+        /// <returns>Creates an uppercase GUID with braces.</returns>
+        string CreateGuid();
+
+        /// <summary>
+        /// Creates a version 3 name-based UUID.
+        /// </summary>
+        /// <param name="namespaceGuid">The namespace UUID.</param>
+        /// <param name="value">The value.</param>
+        /// <returns>The generated GUID for the given namespace and value.</returns>
+        string CreateGuid(Guid namespaceGuid, string value);
+
+        /// <summary>
+        /// Creates a resolved directory.
+        /// </summary>
+        /// <param name="directoryParent">Directory parent identifier.</param>
+        /// <param name="name">Name of directory.</param>
+        /// <returns>Resolved directory.</returns>
+        IResolvedDirectory CreateResolvedDirectory(string directoryParent, string name);
+
+        /// <summary>
+        /// Extracts embedded files.
+        /// </summary>
+        /// <param name="embeddedFiles">Embedded files to extract.</param>
+        /// <returns><c>ITrackedFile</c> for each embedded file extracted.</returns>
+        IReadOnlyList<ITrackedFile> ExtractEmbeddedFiles(IEnumerable<IExpectedExtractFile> embeddedFiles);
+
+        /// <summary>
+        /// Generate an identifier by hashing data from the row.
+        /// </summary>
+        /// <param name="prefix">Three letter or less prefix for generated row identifier.</param>
+        /// <param name="args">Information to hash.</param>
+        /// <returns>The generated identifier.</returns>
+        string GenerateIdentifier(string prefix, params string[] args);
+
+        /// <summary>
+        /// Validates path is relative and canonicalizes it.
+        /// For example, "a\..\c\.\d.exe" => "c\d.exe".
+        /// </summary>
+        /// <param name="sourceLineNumbers"></param>
+        /// <param name="elementName"></param>
+        /// <param name="attributeName"></param>
+        /// <param name="relativePath"></param>
+        /// <returns>The original value if not relative, otherwise the canonicalized relative path.</returns>
+        string GetCanonicalRelativePath(SourceLineNumber sourceLineNumbers, string elementName, string attributeName, string relativePath);
+
+        /// <summary>
+        /// Gets a valid code page from the given web name or integer value.
+        /// </summary>
+        /// <param name="value">A code page web name or integer value as a string.</param>
+        /// <param name="allowNoChange">Whether to allow -1 which does not change the database code pages. This may be the case with wxl files.</param>
+        /// <param name="onlyAnsi">Whether to allow Unicode (UCS) or UTF code pages.</param>
+        /// <param name="sourceLineNumbers">Source line information for the current authoring.</param>
+        /// <returns>A valid code page number.</returns>
+        /// <exception cref="ArgumentOutOfRangeException">The value is an integer less than 0 or greater than 65535.</exception>
+        /// <exception cref="ArgumentNullException"><paramref name="value"/> is null.</exception>
+        /// <exception cref="NotSupportedException">The value doesn't not represent a valid code page name or integer value.</exception>
+        /// <exception cref="WixException">The code page is invalid for summary information.</exception>
+        int GetValidCodePage(string value, bool allowNoChange = false, bool onlyAnsi = false, SourceLineNumber sourceLineNumbers = null);
+
+        /// <summary>
+        /// Get a source/target and short/long file name from an MSI Filename column.
+        /// </summary>
+        /// <param name="value">The Filename value.</param>
+        /// <param name="source">true to get a source name; false to get a target name</param>
+        /// <param name="longName">true to get a long name; false to get a short name</param>
+        /// <returns>The name.</returns>
+        string GetMsiFileName(string value, bool source, bool longName);
+
+        /// <summary>
+        /// Verifies if an identifier is a valid binder variable name.
+        /// </summary>
+        /// <param name="variable">Binder variable name to verify.</param>
+        /// <returns>True if the identifier is a valid binder variable name.</returns>
+        bool IsValidBinderVariable(string variable);
+
+        /// <summary>
+        /// Verifies the given string is a valid 4-part version module or bundle version.
+        /// </summary>
+        /// <param name="version">The version to verify.</param>
+        /// <returns>True if version is a valid module or bundle version.</returns>
+        bool IsValidFourPartVersion(string version);
+
+        /// <summary>
+        /// Determines if value is a valid identifier.
+        /// </summary>
+        /// <param name="id">Identifier to validate.</param>
+        /// <returns>True if valid identifier, otherwise false.</returns>
+        bool IsValidIdentifier(string id);
+
+        /// <summary>
+        /// Verifies the given string is a valid long filename.
+        /// </summary>
+        /// <param name="filename">The filename to verify.</param>
+        /// <param name="allowWildcards">Allow wildcards in the filename.</param>
+        /// <param name="allowRelative">Allow long file name to be a relative path.</param>
+        /// <returns>True if filename is a valid long filename.</returns>
+        bool IsValidLongFilename(string filename, bool allowWildcards, bool allowRelative);
+
+        /// <summary>
+        /// Verifies the given string is a valid short filename.
+        /// </summary>
+        /// <param name="filename">The filename to verify.</param>
+        /// <param name="allowWildcards">Allow wildcards in the filename.</param>
+        /// <returns>True if filename is a valid short filename.</returns>
+        bool IsValidShortFilename(string filename, bool allowWildcards);
+
+        /// <summary>
+        /// Resolve delayed fields.
+        /// </summary>
+        /// <param name="delayedFields">The fields which had resolution delayed.</param>
+        /// <param name="variableCache">The cached variable values used when resolving delayed fields.</param>
+        void ResolveDelayedFields(IEnumerable<IDelayedField> delayedFields, Dictionary<string, string> variableCache);
+
+        /// <summary>
+        /// Get the source/target and short/long file names from an MSI Filename column.
+        /// </summary>
+        /// <param name="value">The Filename value.</param>
+        /// <returns>An array of strings of length 4. The contents are: short target, long target, short source, and long source.</returns>
+        /// <remarks>
+        /// If any particular file name part is not parsed, its set to null in the appropriate location of the returned array of strings.
+        /// Thus the returned array will always be of length 4.
+        /// </remarks>
+        string[] SplitMsiFileName(string value);
+
+        /// <summary>
+        /// Creates a tracked file.
+        /// </summary>
+        /// <param name="path">Destination path for the build output.</param>
+        /// <param name="type">Type of tracked file to create.</param>
+        /// <param name="sourceLineNumbers">Optional source line numbers that requested the tracked file.</param>
+        ITrackedFile TrackFile(string path, TrackedFileType type, SourceLineNumber sourceLineNumbers = null);
+    }
+}
diff --git a/src/api/wix/WixToolset.Extensibility/Services/IBurnBackendHelper.cs b/src/api/wix/WixToolset.Extensibility/Services/IBurnBackendHelper.cs
new file mode 100644
index 00000000..ef5fcc65
--- /dev/null
+++ b/src/api/wix/WixToolset.Extensibility/Services/IBurnBackendHelper.cs
@@ -0,0 +1,50 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved. Licensed under the Microsoft Reciprocal License. See LICENSE.TXT file in the project root for full license information.
+
+namespace WixToolset.Extensibility.Services
+{
+    using WixToolset.Data;
+
+    /// <summary>
+    /// Interface provided to help Burn backend extensions.
+    /// </summary>
+    public interface IBurnBackendHelper : IBackendHelper
+    {
+        /// <summary>
+        /// Adds the given XML to the BootstrapperApplicationData manifest.
+        /// </summary>
+        /// <param name="xml">A valid XML fragment.</param>
+        void AddBootstrapperApplicationData(string xml);
+
+        /// <summary>
+        /// Adds an XML element for the given symbol to the BootstrapperApplicationData manifest.
+        /// The symbol's name is used for the element's name.
+        /// All of the symbol's fields are used for the element's attributes.
+        /// </summary>
+        /// <param name="symbol">The symbol to create the element from.</param>
+        /// <param name="symbolIdIsIdAttribute">
+        /// If true and the symbol has an Id,
+        /// then an Id attribute is created with a value of the symbol's Id.
+        /// </param>
+        void AddBootstrapperApplicationData(IntermediateSymbol symbol, bool symbolIdIsIdAttribute = false);
+
+        /// <summary>
+        /// Adds the given XML to the BundleExtensionData manifest for the given bundle extension.
+        /// </summary>
+        /// <param name="extensionId">The bundle extension's id.</param>
+        /// <param name="xml">A valid XML fragment.</param>
+        void AddBundleExtensionData(string extensionId, string xml);
+
+        /// <summary>
+        /// Adds an XML element for the given symbol to the BundleExtensionData manifest for the given bundle extension.
+        /// The symbol's name is used for the element's name.
+        /// All of the symbol's fields are used for the element's attributes.
+        /// </summary>
+        /// <param name="extensionId">The bundle extension's id.</param>
+        /// <param name="symbol">The symbol to create the element from.</param>
+        /// <param name="symbolIdIsIdAttribute">
+        /// If true and the symbol has an Id,
+        /// then an Id attribute is created with a value of the symbol's Id.
+        /// </param>
+        void AddBundleExtensionData(string extensionId, IntermediateSymbol symbol, bool symbolIdIsIdAttribute = false);
+    }
+}
diff --git a/src/api/wix/WixToolset.Extensibility/Services/ICommandLine.cs b/src/api/wix/WixToolset.Extensibility/Services/ICommandLine.cs
new file mode 100644
index 00000000..2b841af0
--- /dev/null
+++ b/src/api/wix/WixToolset.Extensibility/Services/ICommandLine.cs
@@ -0,0 +1,33 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved. Licensed under the Microsoft Reciprocal License. See LICENSE.TXT file in the project root for full license information.
+
+namespace WixToolset.Extensibility.Services
+{
+    using WixToolset.Extensibility.Data;
+
+    /// <summary>
+    /// Command-line parsing mechanism.
+    /// </summary>
+    public interface ICommandLine
+    {
+        /// <summary>
+        /// Simple way to parse arguments and create a command.
+        /// </summary>
+        /// <param name="args">Unparsed arguments.</param>
+        /// <returns>Command if the command-line arguments can be parsed, otherwise null.</returns>
+        ICommandLineCommand CreateCommand(string[] args);
+
+        /// <summary>
+        /// Simple way to parse arguments and create a command.
+        /// </summary>
+        /// <param name="commandLine">Unparsed arguments.</param>
+        /// <returns>Command if the command-line arguments can be parsed, otherwise null.</returns>
+        ICommandLineCommand CreateCommand(string commandLine);
+
+        /// <summary>
+        /// Creates a command from populated arguments.
+        /// </summary>
+        /// <param name="arguments">Parsed arguments.</param>
+        /// <returns>Command if the command-line arguments can be parsed, otherwise null.</returns>
+        ICommandLineCommand ParseStandardCommandLine(ICommandLineArguments arguments);
+    }
+}
diff --git a/src/api/wix/WixToolset.Extensibility/Services/ICommandLineParser.cs b/src/api/wix/WixToolset.Extensibility/Services/ICommandLineParser.cs
new file mode 100644
index 00000000..cd17f100
--- /dev/null
+++ b/src/api/wix/WixToolset.Extensibility/Services/ICommandLineParser.cs
@@ -0,0 +1,40 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved. Licensed under the Microsoft Reciprocal License. See LICENSE.TXT file in the project root for full license information.
+
+namespace WixToolset.Extensibility.Services
+{
+    using System.Collections.Generic;
+    using WixToolset.Data;
+
+#pragma warning disable 1591 // TODO: add documentation
+    public interface ICommandLineParser
+    {
+        string ErrorArgument { get; }
+
+        /// <summary>
+        /// Validates that a valid switch (starts with "/" or "-"), and returns a bool indicating its validity
+        /// </summary>
+        /// <param name="arg">The string check.</param>
+        /// <returns>True if a valid switch, otherwise false.</returns>
+        bool IsSwitch(string arg);
+
+        string GetArgumentAsFilePathOrError(string argument, string fileType);
+
+        void GetArgumentAsFilePathOrError(string argument, string fileType, IList<string> paths);
+
+        string GetNextArgumentOrError(string commandLineSwitch);
+
+        bool GetNextArgumentOrError(string commandLineSwitch, IList<string> argument);
+
+        string GetNextArgumentAsDirectoryOrError(string commandLineSwitch);
+
+        bool GetNextArgumentAsDirectoryOrError(string commandLineSwitch, IList<string> directories);
+
+        string GetNextArgumentAsFilePathOrError(string commandLineSwitch);
+
+        bool GetNextArgumentAsFilePathOrError(string commandLineSwitch, string fileType, IList<string> paths);
+
+        void ReportErrorArgument(string argument, Message message = null);
+
+        bool TryGetNextSwitchOrArgument(out string arg);
+    }
+}
diff --git a/src/api/wix/WixToolset.Extensibility/Services/IExtensionManager.cs b/src/api/wix/WixToolset.Extensibility/Services/IExtensionManager.cs
new file mode 100644
index 00000000..8e49c38d
--- /dev/null
+++ b/src/api/wix/WixToolset.Extensibility/Services/IExtensionManager.cs
@@ -0,0 +1,42 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved. Licensed under the Microsoft Reciprocal License. See LICENSE.TXT file in the project root for full license information.
+
+namespace WixToolset.Extensibility.Services
+{
+    using System.Collections.Generic;
+    using System.Reflection;
+
+    /// <summary>
+    /// Loads extensions and uses the extensions' factories to provide services.
+    /// </summary>
+    public interface IExtensionManager
+    {
+        /// <summary>
+        /// Adds an extension assembly directly to the manager.
+        /// </summary>
+        /// <param name="extensionAssembly">Extension assembly.</param>
+        void Add(Assembly extensionAssembly);
+
+        /// <summary>
+        /// Loads an extension assembly from an extension reference string.
+        /// </summary>
+        /// <param name="extensionReference">Reference to the extension.</param>
+        /// <returns>The loaded assembly. This assembly can be ignored since the extension manager maintains the list of loaded assemblies internally.</returns>
+        /// <remarks>
+        /// <paramref name="extensionReference"/> can be in several different forms:
+        /// <list type="number">
+        /// <item><term>Full path to an extension file (C:\MyExtensions\MyExtension.Example.wixext.dll)</term></item>
+        /// <item><term>Reference to latest version of an extension in the cache (MyExtension.Example.wixext)</term></item>
+        /// <item><term>Versioned reference to specific extension in the cache (MyExtension.Example.wixext/1.0.2)</term></item>
+        /// <item><term>Relative path to an extension file (..\..\MyExtensions\MyExtension.Example.wixext.dll)</term></item>
+        /// </list>
+        /// </remarks>
+        void Load(string extensionReference);
+
+        /// <summary>
+        /// Gets extensions of specified type from factories loaded into the extension manager.
+        /// </summary>
+        /// <typeparam name="T">Type of extension to get.</typeparam>
+        /// <returns>Extensions of the specified type.</returns>
+        IReadOnlyCollection<T> GetServices<T>() where T : class;
+    }
+}
diff --git a/src/api/wix/WixToolset.Extensibility/Services/IMessaging.cs b/src/api/wix/WixToolset.Extensibility/Services/IMessaging.cs
new file mode 100644
index 00000000..fe77f2a4
--- /dev/null
+++ b/src/api/wix/WixToolset.Extensibility/Services/IMessaging.cs
@@ -0,0 +1,73 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved. Licensed under the Microsoft Reciprocal License. See LICENSE.TXT file in the project root for full license information.
+
+namespace WixToolset.Extensibility.Services
+{
+    using WixToolset.Data;
+
+    /// <summary>
+    /// Interface for handling messages (error/warning/verbose).
+    /// </summary>
+    public interface IMessaging
+    {
+        /// <summary>
+        /// Indicates whether an error has been found.
+        /// </summary>
+        /// <value>A bool indicating whether an error has been found.</value>
+        bool EncounteredError { get; }
+
+        /// <summary>
+        /// Gets the last error code encountered during messaging.
+        /// </summary>
+        /// <value>The exit code for the process.</value>
+        int LastErrorNumber { get; }
+
+        /// <summary>
+        /// Gets or sets the option to show verbose messages.
+        /// </summary>
+        /// <value>The option to show verbose messages.</value>
+        bool ShowVerboseMessages { get; set; }
+
+        /// <summary>
+        /// Gets or sets the option to suppress all warning messages.
+        /// </summary>
+        /// <value>The option to suppress all warning messages.</value>
+        bool SuppressAllWarnings { get; set; }
+
+        /// <summary>
+        /// Gets and sets the option to treat warnings as errors.
+        /// </summary>
+        /// <value>The option to treat warnings as errors.</value>
+        bool WarningsAsError { get; set; }
+
+        /// <summary>
+        /// Sets the listener for messaging.
+        /// </summary>
+        /// <param name="listener"></param>
+        void SetListener(IMessageListener listener);
+
+        /// <summary>
+        /// Adds a warning message id to be elevated to an error message.
+        /// </summary>
+        /// <param name="warningNumber">Id of the message to elevate.</param>
+        void ElevateWarningMessage(int warningNumber);
+
+        /// <summary>
+        /// Adds a warning message id to be suppressed in message output.
+        /// </summary>
+        /// <param name="warningNumber">Id of the message to suppress.</param>
+        void SuppressWarningMessage(int warningNumber);
+
+        /// <summary>
+        /// Sends a message with the given arguments.
+        /// </summary>
+        /// <param name="message">Message to write.</param>
+        void Write(Message message);
+
+        /// <summary>
+        /// Sends a message with the given arguments.
+        /// </summary>
+        /// <param name="message">Message to write.</param>
+        /// <param name="verbose">Indicates where to write a verbose message.</param>
+        void Write(string message, bool verbose = false);
+    }
+}
diff --git a/src/api/wix/WixToolset.Extensibility/Services/IParseHelper.cs b/src/api/wix/WixToolset.Extensibility/Services/IParseHelper.cs
new file mode 100644
index 00000000..fbe5aae4
--- /dev/null
+++ b/src/api/wix/WixToolset.Extensibility/Services/IParseHelper.cs
@@ -0,0 +1,466 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved. Licensed under the Microsoft Reciprocal License. See LICENSE.TXT file in the project root for full license information.
+
+namespace WixToolset.Extensibility.Services
+{
+    using System;
+    using System.Collections.Generic;
+    using System.Xml.Linq;
+    using WixToolset.Data;
+    using WixToolset.Data.Symbols;
+    using WixToolset.Data.WindowsInstaller;
+    using WixToolset.Extensibility.Data;
+
+    /// <summary>
+    /// Interface provided to help compiler extensions parse.
+    /// </summary>
+    public interface IParseHelper
+    {
+        /// <summary>
+        /// Creates a version 3 name-based UUID.
+        /// </summary>
+        /// <param name="namespaceGuid">The namespace UUID.</param>
+        /// <param name="value">The value.</param>
+        /// <returns>The generated GUID for the given namespace and value.</returns>
+        string CreateGuid(Guid namespaceGuid, string value);
+
+        /// <summary>
+        /// Create an identifier by hashing data from the row.
+        /// </summary>
+        /// <param name="prefix">Three letter or less prefix for generated row identifier.</param>
+        /// <param name="args">Information to hash.</param>
+        /// <returns>The new identifier.</returns>
+        Identifier CreateIdentifier(string prefix, params string[] args);
+
+        /// <summary>
+        /// Create an identifier based on passed file name
+        /// </summary>
+        /// <param name="filename">File name to generate identifier from</param>
+        /// <returns>The new identifier.</returns>
+        Identifier CreateIdentifierFromFilename(string filename);
+
+        /// <summary>
+        /// Append a suffix to the given name based on the current platform.
+        /// If the current platform is not in the supported platforms, then it returns null.
+        /// </summary>
+        /// <param name="name">The base name for the identifier.</param>
+        /// <param name="currentPlatform">The platform being compiled.</param>
+        /// <param name="supportedPlatforms">The platforms for which there are specialized implementations.</param>
+        /// <returns>The generated identifier value, or null if the current platform isn't supported.</returns>
+        string CreateIdentifierValueFromPlatform(string name, Platform currentPlatform, BurnPlatforms supportedPlatforms);
+
+        /// <summary>
+        /// Creates a symbol in the section.
+        /// </summary>
+        /// <param name="section">Section to add the new symbol to.</param>
+        /// <param name="sourceLineNumbers">Source and line number of current symbol.</param>
+        /// <param name="symbolName">Name of symbol definition.</param>
+        /// <param name="identifier">Optional identifier for the symbol.</param>
+        /// <returns>New symbol.</returns>
+        IntermediateSymbol CreateSymbol(IntermediateSection section, SourceLineNumber sourceLineNumbers, string symbolName, Identifier identifier = null);
+
+        /// <summary>
+        /// Creates a symbol in the section.
+        /// </summary>
+        /// <param name="section">Section to add the new symbol to.</param>
+        /// <param name="sourceLineNumbers">Source and line number of current symbol.</param>
+        /// <param name="symbolDefinition">Symbol definition to create from.</param>
+        /// <param name="identifier">Optional identifier for the symbol.</param>
+        /// <returns>New symbol.</returns>
+        IntermediateSymbol CreateSymbol(IntermediateSection section, SourceLineNumber sourceLineNumbers, IntermediateSymbolDefinition symbolDefinition, Identifier identifier = null);
+
+        /// <summary>
+        /// Creates a directory row from a name.
+        /// </summary>
+        /// <param name="section">Section to add the new symbol to.</param>
+        /// <param name="sourceLineNumbers">Source line information.</param>
+        /// <param name="id">Optional identifier for the new row.</param>
+        /// <param name="parentId">Optional identifier for the parent row.</param>
+        /// <param name="name">Long name of the directory.</param>
+        /// <param name="shortName">Optional short name of the directory.</param>
+        /// <param name="sourceName">Optional source name for the directory.</param>
+        /// <param name="shortSourceName">Optional short source name for the directory.</param>
+        /// <returns>Identifier for the newly created row.</returns>
+        Identifier CreateDirectorySymbol(IntermediateSection section, SourceLineNumber sourceLineNumbers, Identifier id, string parentId, string name, string shortName = null, string sourceName = null, string shortSourceName = null);
+
+        /// <summary>
+        /// Creates directories using the inline directory syntax.
+        /// </summary>
+        /// <param name="section">Section to add the new symbol to.</param>
+        /// <param name="sourceLineNumbers">Source line information.</param>
+        /// <param name="attribute">Attribute containing the inline syntax.</param>
+        /// <param name="parentId">Optional identifier of parent directory.</param>
+        /// <param name="inlineSyntax">Optional inline syntax to override attribute's value.</param>
+        /// <param name="sectionCachedInlinedDirectoryIds">Mapping of inline directory syntax to ids for the section.</param>
+        /// <returns>Identifier of the leaf directory created.</returns>
+        string CreateDirectoryReferenceFromInlineSyntax(IntermediateSection section, SourceLineNumber sourceLineNumbers, XAttribute attribute, string parentId, string inlineSyntax, IDictionary<string, string> sectionCachedInlinedDirectoryIds);
+
+        /// <summary>
+        /// Creates a Registry symbol in the active section.
+        /// </summary>
+        /// <param name="section">Active section.</param>
+        /// <param name="sourceLineNumbers">Source and line number of the current symbol.</param>
+        /// <param name="root">The registry entry root.</param>
+        /// <param name="key">The registry entry key.</param>
+        /// <param name="name">The registry entry name.</param>
+        /// <param name="value">The registry entry value.</param>
+        /// <param name="componentId">The component which will control installation/uninstallation of the registry entry.</param>
+        /// <param name="escapeLeadingHash">If true, "escape" leading '#' characters so the value is written as a REG_SZ.</param>
+        Identifier CreateRegistrySymbol(IntermediateSection section, SourceLineNumber sourceLineNumbers, RegistryRootType root, string key, string name, string value, string componentId, bool escapeLeadingHash);
+
+        /// <summary>
+        /// Create a WixSimpleReference symbol in the active section.
+        /// </summary>
+        /// <param name="section">Active section.</param>
+        /// <param name="sourceLineNumbers">Source line information for the row.</param>
+        /// <param name="symbolName">The symbol name of the simple reference.</param>
+        /// <param name="primaryKey">The primary key of the simple reference.</param>
+        void CreateSimpleReference(IntermediateSection section, SourceLineNumber sourceLineNumbers, string symbolName, string primaryKey);
+
+        /// <summary>
+        /// Create a WixSimpleReference symbol in the active section.
+        /// </summary>
+        /// <param name="section">Active section.</param>
+        /// <param name="sourceLineNumbers">Source line information for the row.</param>
+        /// <param name="symbolName">The symbol name of the simple reference.</param>
+        /// <param name="primaryKeys">The primary keys of the simple reference.</param>
+        void CreateSimpleReference(IntermediateSection section, SourceLineNumber sourceLineNumbers, string symbolName, params string[] primaryKeys);
+
+        /// <summary>
+        /// Create a WixSimpleReference symbol in the active section.
+        /// </summary>
+        /// <param name="section">Active section.</param>
+        /// <param name="sourceLineNumbers">Source line information for the row.</param>
+        /// <param name="symbolDefinition">The symbol definition of the simple reference.</param>
+        /// <param name="primaryKey">The primary key of the simple reference.</param>
+        void CreateSimpleReference(IntermediateSection section, SourceLineNumber sourceLineNumbers, IntermediateSymbolDefinition symbolDefinition, string primaryKey);
+
+        /// <summary>
+        /// Create a WixSimpleReference symbol in the active section.
+        /// </summary>
+        /// <param name="section">Active section.</param>
+        /// <param name="sourceLineNumbers">Source line information for the row.</param>
+        /// <param name="symbolDefinition">The symbol definition of the simple reference.</param>
+        /// <param name="primaryKeys">The primary keys of the simple reference.</param>
+        void CreateSimpleReference(IntermediateSection section, SourceLineNumber sourceLineNumbers, IntermediateSymbolDefinition symbolDefinition, params string[] primaryKeys);
+
+        /// <summary>
+        /// Create a reference in the specified section for a custom action specialized for specific platforms,
+        /// given standard prefixes for naming and suffixes for platforms.
+        /// </summary>
+        /// <param name="sourceLineNumbers">Source line information.</param>
+        /// <param name="section">Section to create the reference in.</param>
+        /// <param name="customAction">The custom action base name.</param>
+        /// <param name="platform">The platform being compiled.</param>
+        /// <param name="supportedPlatforms">The platforms for which there are specialized custom actions.</param>
+        void CreateCustomActionReference(SourceLineNumber sourceLineNumbers, IntermediateSection section, string customAction, Platform platform, CustomActionPlatforms supportedPlatforms);
+
+        /// <summary>
+        /// Creates WixComplexReference and WixGroup symbols in the active section.
+        /// </summary>
+        /// <param name="section">Section to create the reference in.</param>
+        /// <param name="sourceLineNumbers">Source line information.</param>
+        /// <param name="parentType">The parent type.</param>
+        /// <param name="parentId">The parent id.</param>
+        /// <param name="parentLanguage">The parent language.</param>
+        /// <param name="childType">The child type.</param>
+        /// <param name="childId">The child id.</param>
+        /// <param name="isPrimary">Whether the child is primary.</param>
+        void CreateComplexReference(IntermediateSection section, SourceLineNumber sourceLineNumbers, ComplexReferenceParentType parentType, string parentId, string parentLanguage, ComplexReferenceChildType childType, string childId, bool isPrimary);
+
+        /// <summary>
+        /// A symbol in the WixGroup table is added for this child node and its parent node.
+        /// </summary>
+        /// <param name="section">Section to create the reference in.</param>
+        /// <param name="sourceLineNumbers">Source line information for the row.</param>
+        /// <param name="parentType">Type of child's complex reference parent.</param>
+        /// <param name="parentId">Id of the parenet node.</param>
+        /// <param name="childType">Complex reference type of child</param>
+        /// <param name="childId">Id of the Child Node.</param>
+        void CreateWixGroupSymbol(IntermediateSection section, SourceLineNumber sourceLineNumbers, ComplexReferenceParentType parentType, string parentId, ComplexReferenceChildType childType, string childId);
+
+        /// <summary>
+        /// Creates a symbol in the WixSearch table.
+        /// </summary>
+        /// <param name="section">Section to create the reference in.</param>
+        /// <param name="sourceLineNumbers">Source line number for the search element.</param>
+        /// <param name="elementName">Name of search element.</param>
+        /// <param name="id">Identifier of the search.</param>
+        /// <param name="variable">The Burn variable to store the result into.</param>
+        /// <param name="condition">A condition to test before evaluating the search.</param>
+        /// <param name="after">The search that this one will execute after.</param>
+        /// <param name="bundleExtensionId">The id of the bundle extension that handles this search.</param>
+        void CreateWixSearchSymbol(IntermediateSection section, SourceLineNumber sourceLineNumbers, string elementName, Identifier id, string variable, string condition, string after, string bundleExtensionId);
+
+        /// <summary>
+        ///
+        /// </summary>
+        /// <param name="section">Section to create the reference in.</param>
+        /// <param name="sourceLineNumbers">Source line number for the parent element.</param>
+        /// <param name="id">Identifier of the search (key into the WixSearch table)</param>
+        /// <param name="parentId">Identifier of the search that comes before (key into the WixSearch table)</param>
+        /// <param name="attributes">Further details about the relation between id and parentId.</param>
+        void CreateWixSearchRelationSymbol(IntermediateSection section, SourceLineNumber sourceLineNumbers, Identifier id, string parentId, int attributes);
+
+        /// <summary>
+        /// Checks if the string contains a property (i.e. "foo[Property]bar")
+        /// </summary>
+        /// <param name="possibleProperty">String to evaluate for properties.</param>
+        /// <returns>True if a property is found in the string.</returns>
+        bool ContainsProperty(string possibleProperty);
+
+        /// <summary>
+        /// Add the appropriate symbols to make sure that the given table shows up in the resulting output.
+        /// </summary>
+        /// <param name="section">Active section.</param>
+        /// <param name="sourceLineNumbers">Source line numbers.</param>
+        /// <param name="tableName">Name of the table to ensure existance of.</param>
+        void EnsureTable(IntermediateSection section, SourceLineNumber sourceLineNumbers, string tableName);
+
+        /// <summary>
+        /// Add the appropriate symbols to make sure that the given table shows up in the resulting output.
+        /// </summary>
+        /// <param name="section">Active section.</param>
+        /// <param name="sourceLineNumbers">Source line numbers.</param>
+        /// <param name="tableDefinition">Definition of the table to ensure existance of.</param>
+        void EnsureTable(IntermediateSection section, SourceLineNumber sourceLineNumbers, TableDefinition tableDefinition);
+
+        /// <summary>
+        /// Get an attribute value and displays an error if the value is empty by default.
+        /// </summary>
+        /// <param name="sourceLineNumbers">Source line information about the owner element.</param>
+        /// <param name="attribute">The attribute containing the value to get.</param>
+        /// <param name="emptyRule">A rule for the contents of the value. If the contents do not follow the rule, an error is thrown.</param>
+        /// <returns>The attribute's value.</returns>
+        string GetAttributeValue(SourceLineNumber sourceLineNumbers, XAttribute attribute, EmptyRule emptyRule = EmptyRule.CanBeWhitespaceOnly);
+
+        /// <summary>
+        /// Get a guid attribute value and displays an error for an illegal guid value.
+        /// </summary>
+        /// <param name="sourceLineNumbers">Source line information about the owner element.</param>
+        /// <param name="attribute">The attribute containing the value to get.</param>
+        /// <param name="generatable">Determines whether the guid can be automatically generated.</param>
+        /// <param name="canBeEmpty">If true, no error is raised on empty value. If false, an error is raised.</param>
+        /// <returns>The attribute's guid value or a special value if an error occurred.</returns>
+        string GetAttributeGuidValue(SourceLineNumber sourceLineNumbers, XAttribute attribute, bool generatable = false, bool canBeEmpty = false);
+
+        /// <summary>
+        /// Get an identifier attribute value and displays an error for an illegal identifier value.
+        /// </summary>
+        /// <param name="sourceLineNumbers">Source line information about the owner element.</param>
+        /// <param name="attribute">The attribute containing the value to get.</param>
+        /// <returns>The attribute's identifier value or a special value if an error occurred.</returns>
+        Identifier GetAttributeIdentifier(SourceLineNumber sourceLineNumbers, XAttribute attribute);
+
+        /// <summary>
+        /// Get an identifier attribute value and displays an error for an illegal identifier value.
+        /// </summary>
+        /// <param name="sourceLineNumbers">Source line information about the owner element.</param>
+        /// <param name="attribute">The attribute containing the value to get.</param>
+        /// <returns>The attribute's identifier value or a special value if an error occurred.</returns>
+        string GetAttributeIdentifierValue(SourceLineNumber sourceLineNumbers, XAttribute attribute);
+
+        /// <summary>
+        /// Get an integer attribute value and displays an error for an illegal integer value.
+        /// </summary>
+        /// <param name="sourceLineNumbers">Source line information about the owner element.</param>
+        /// <param name="attribute">The attribute containing the value to get.</param>
+        /// <param name="minimum">The minimum legal value.</param>
+        /// <param name="maximum">The maximum legal value.</param>
+        /// <returns>The attribute's integer value or a special value if an error occurred during conversion.</returns>
+        int GetAttributeIntegerValue(SourceLineNumber sourceLineNumbers, XAttribute attribute, int minimum, int maximum);
+
+        /// <summary>
+        /// Get a long integral attribute value and displays an error for an illegal long value.
+        /// </summary>
+        /// <param name="sourceLineNumbers">Source line information about the owner element.</param>
+        /// <param name="attribute">The attribute containing the value to get.</param>
+        /// <param name="minimum">The minimum legal value.</param>
+        /// <param name="maximum">The maximum legal value.</param>
+        /// <returns>The attribute's long value or a special value if an error occurred during conversion.</returns>
+        long GetAttributeLongValue(SourceLineNumber sourceLineNumbers, XAttribute attribute, long minimum, long maximum);
+
+        /// <summary>
+        /// Gets a long filename value and displays an error for an illegal long filename value.
+        /// </summary>
+        /// <param name="sourceLineNumbers">Source line information about the owner element.</param>
+        /// <param name="attribute">The attribute containing the value to get.</param>
+        /// <param name="allowWildcards">true if wildcards are allowed in the filename.</param>
+        /// <param name="allowRelative">true if relative paths are allowed in the filename.</param>
+        /// <returns>The attribute's long filename value.</returns>
+        string GetAttributeLongFilename(SourceLineNumber sourceLineNumbers, XAttribute attribute, bool allowWildcards = false, bool allowRelative = false);
+
+        /// <summary>
+        /// Gets a RegistryRootType value and displays an error for an illegal value.
+        /// </summary>
+        /// <param name="sourceLineNumbers">Source line information about the owner element.</param>
+        /// <param name="attribute">The attribute containing the value to get.</param>
+        /// <param name="allowHkmu">Whether HKMU is returned as -1 (true), or treated as an error (false).</param>
+        /// <returns>The attribute's RegisitryRootType value.</returns>
+        RegistryRootType? GetAttributeRegistryRootValue(SourceLineNumber sourceLineNumbers, XAttribute attribute, bool allowHkmu);
+
+        /// <summary>
+        /// Gets a version value or possibly a binder variable and displays an error for an illegal version value.
+        /// </summary>
+        /// <param name="sourceLineNumbers">Source line information about the owner element.</param>
+        /// <param name="attribute">The attribute containing the value to get.</param>
+        /// <returns>The attribute's version value.</returns>
+        string GetAttributeVersionValue(SourceLineNumber sourceLineNumbers, XAttribute attribute);
+
+        /// <summary>
+        /// Gets a yes/no value and displays an error for an illegal yes/no value.
+        /// </summary>
+        /// <param name="sourceLineNumbers">Source line information about the owner element.</param>
+        /// <param name="attribute">The attribute containing the value to get.</param>
+        /// <returns>The attribute's YesNoType value.</returns>
+        YesNoType GetAttributeYesNoValue(SourceLineNumber sourceLineNumbers, XAttribute attribute);
+
+        /// <summary>
+        /// Gets a yes/no/default value and displays an error for an illegal yes/no/default value.
+        /// </summary>
+        /// <param name="sourceLineNumbers">Source line information about the owner element.</param>
+        /// <param name="attribute">The attribute containing the value to get.</param>
+        /// <returns>The attribute's YesNoType value.</returns>
+        YesNoDefaultType GetAttributeYesNoDefaultValue(SourceLineNumber sourceLineNumbers, XAttribute attribute);
+
+        /// <summary>
+        /// Validates path is relative and canonicalizes it.
+        /// For example, "a\..\c\.\d.exe" => "c\d.exe".
+        /// </summary>
+        /// <param name="sourceLineNumbers"></param>
+        /// <param name="elementName"></param>
+        /// <param name="attributeName"></param>
+        /// <param name="relativePath"></param>
+        /// <returns>The original value if not relative, otherwise the canonicalized relative path.</returns>
+        string GetCanonicalRelativePath(SourceLineNumber sourceLineNumbers, string elementName, string attributeName, string relativePath);
+
+        /// <summary>
+        /// Gets a source line number for an element.
+        /// </summary>
+        /// <param name="element">Element to get source line number.</param>
+        /// <returns>Source line number.</returns>
+        SourceLineNumber GetSourceLineNumbers(XElement element);
+
+        /// <summary>
+        /// Gets node's inner text and ensure's it is safe for use in a condition by trimming any extra whitespace.
+        /// </summary>
+        /// <param name="node">The node to ensure inner text is a condition.</param>
+        /// <returns>The value converted into a safe condition.</returns>
+        [Obsolete]
+        string GetConditionInnerText(XElement node);
+
+        /// <summary>
+        /// Get an element's inner text and trims any extra whitespace.
+        /// </summary>
+        /// <param name="element">The element with inner text to be trimmed.</param>
+        /// <returns>The node's inner text trimmed.</returns>
+        [Obsolete]
+        string GetTrimmedInnerText(XElement element);
+
+        /// <summary>
+        /// Validates that the element does not contain inner text.
+        /// </summary>
+        /// <param name="element">Element to check for inner text.</param>
+        void InnerTextDisallowed(XElement element);
+
+        /// <summary>
+        /// Verifies that a value is a legal identifier.
+        /// </summary>
+        /// <param name="value">The value to verify.</param>
+        /// <returns>true if the value is an identifier; false otherwise.</returns>
+        bool IsValidIdentifier(string value);
+
+        /// <summary>
+        /// Verifies if an identifier is a valid loc identifier.
+        /// </summary>
+        /// <param name="identifier">Identifier to verify.</param>
+        /// <returns>True if the identifier is a valid loc identifier.</returns>
+        bool IsValidLocIdentifier(string identifier);
+
+        /// <summary>
+        /// Verifies if a filename is a valid long filename.
+        /// </summary>
+        /// <param name="filename">Filename to verify.</param>
+        /// <param name="allowWildcards">true if wildcards are allowed in the filename.</param>
+        /// <param name="allowRelative">true if relative paths are allowed in the filename.</param>
+        /// <returns>True if the filename is a valid long filename</returns>
+        bool IsValidLongFilename(string filename, bool allowWildcards = false, bool allowRelative = false);
+
+        /// <summary>
+        /// Verifies if a filename is a valid short filename.
+        /// </summary>
+        /// <param name="filename">Filename to verify.</param>
+        /// <param name="allowWildcards">Indicates whether wildcards are allowed in the filename.</param>
+        /// <returns>True if the filename is a valid short filename</returns>
+        bool IsValidShortFilename(string filename, bool allowWildcards);
+
+        /// <summary>
+        /// Attempts to use an extension to parse the attribute.
+        /// </summary>
+        /// <param name="extensions"></param>
+        /// <param name="intermediate">Parent intermediate.</param>
+        /// <param name="section">Parent section.</param>
+        /// <param name="element">Element containing attribute to be parsed.</param>
+        /// <param name="attribute">Attribute to be parsed.</param>
+        /// <param name="context">Extra information about the context in which this element is being parsed.</param>
+        void ParseExtensionAttribute(IEnumerable<ICompilerExtension> extensions, Intermediate intermediate, IntermediateSection section, XElement element, XAttribute attribute, IDictionary<string, string> context = null);
+
+        /// <summary>
+        /// Attempts to use an extension to parse the element.
+        /// </summary>
+        /// <param name="extensions"></param>
+        /// <param name="intermediate">Parent intermediate.</param>
+        /// <param name="section">Parent section.</param>
+        /// <param name="parentElement">Element containing element to be parsed.</param>
+        /// <param name="element">Element to be parsed.</param>
+        /// <param name="context">Extra information about the context in which this element is being parsed.</param>
+        void ParseExtensionElement(IEnumerable<ICompilerExtension> extensions, Intermediate intermediate, IntermediateSection section, XElement parentElement, XElement element, IDictionary<string, string> context = null);
+
+        /// <summary>
+        /// Attempts to use an extension to parse the element, with support for setting component keypath.
+        /// </summary>
+        /// <param name="extensions"></param>
+        /// <param name="intermediate">Parent intermediate.</param>
+        /// <param name="section">Parent section.</param>
+        /// <param name="parentElement">Element containing element to be parsed.</param>
+        /// <param name="element">Element to be parsed.</param>
+        /// <param name="context">Extra information about the context in which this element is being parsed.</param>
+        IComponentKeyPath ParsePossibleKeyPathExtensionElement(IEnumerable<ICompilerExtension> extensions, Intermediate intermediate, IntermediateSection section, XElement parentElement, XElement element, IDictionary<string, string> context);
+
+        /// <summary>
+        /// Process all children of the element looking for extensions and erroring on the unexpected.
+        /// </summary>
+        /// <param name="extensions"></param>
+        /// <param name="intermediate">Parent intermediate.</param>
+        /// <param name="section">Parent section.</param>
+        /// <param name="element">Element to parse children.</param>
+        void ParseForExtensionElements(IEnumerable<ICompilerExtension> extensions, Intermediate intermediate, IntermediateSection section, XElement element);
+
+        /// <summary>
+        /// Schedules an action symbol.
+        /// </summary>
+        /// <param name="section">Section to add the symbol to.</param>
+        /// <param name="sourceLineNumbers">Source line information about the owner element.</param>
+        /// <param name="access">Access modifier for the scheduled action.</param>
+        /// <param name="sequence">Sequence to add the action to.</param>
+        /// <param name="name">Name of action.</param>
+        /// <param name="condition">Optional condition of action.</param>
+        /// <param name="beforeAction">Optional action to schedule before.</param>
+        /// <param name="afterAction">Option action to schedule after.</param>
+        /// <param name="overridable">Optional overridable flag.</param>
+        WixActionSymbol ScheduleActionSymbol(IntermediateSection section, SourceLineNumber sourceLineNumbers, AccessModifier access, SequenceTable sequence, string name, string condition, string beforeAction, string afterAction, bool overridable = false);
+
+        /// <summary>
+        /// Called when the compiler encounters an unexpected attribute.
+        /// </summary>
+        /// <param name="element">Parent element that found unexpected attribute.</param>
+        /// <param name="attribute">Unexpected attribute.</param>
+        void UnexpectedAttribute(XElement element, XAttribute attribute);
+
+        /// <summary>
+        /// Called when the compiler encounters an unexpected child element.
+        /// </summary>
+        /// <param name="parentElement">Parent element that found unexpected child.</param>
+        /// <param name="childElement">Unexpected child element.</param>
+        void UnexpectedElement(XElement parentElement, XElement childElement);
+    }
+}
diff --git a/src/api/wix/WixToolset.Extensibility/Services/IPathResolver.cs b/src/api/wix/WixToolset.Extensibility/Services/IPathResolver.cs
new file mode 100644
index 00000000..64362174
--- /dev/null
+++ b/src/api/wix/WixToolset.Extensibility/Services/IPathResolver.cs
@@ -0,0 +1,43 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved. Licensed under the Microsoft Reciprocal License. See LICENSE.TXT file in the project root for full license information.
+
+namespace WixToolset.Extensibility.Services
+{
+    using System.Collections.Generic;
+    using WixToolset.Data;
+    using WixToolset.Extensibility.Data;
+
+    /// <summary>
+    /// Support for processing paths.
+    /// </summary>
+    public interface IPathResolver
+    {
+        /// <summary>
+        /// Get the canonical source path of a directory.
+        /// </summary>
+        /// <param name="directories">All cached directories.</param>
+        /// <param name="componentIdGenSeeds">Hash table of Component GUID generation seeds indexed by directory id.</param>
+        /// <param name="directory">Directory identifier.</param>
+        /// <param name="platform">Current platform.</param>
+        /// <returns>Source path of a directory.</returns>
+        string GetCanonicalDirectoryPath(Dictionary<string, IResolvedDirectory> directories, Dictionary<string, string> componentIdGenSeeds, string directory, Platform platform);
+
+        /// <summary>
+        /// Get the source path of a directory.
+        /// </summary>
+        /// <param name="directories">All cached directories.</param>
+        /// <param name="directory">Directory identifier.</param>
+        /// <returns>Source path of a directory.</returns>
+        string GetDirectoryPath(Dictionary<string, IResolvedDirectory> directories, string directory);
+
+        /// <summary>
+        /// Gets the source path of a file.
+        /// </summary>
+        /// <param name="directories">All cached directories in <see cref="IResolvedDirectory"/>.</param>
+        /// <param name="directoryId">Parent directory identifier.</param>
+        /// <param name="fileName">File name (in long|source format).</param>
+        /// <param name="compressed">Specifies the package is compressed.</param>
+        /// <param name="useLongName">Specifies the package uses long file names.</param>
+        /// <returns>Source path of file relative to package directory.</returns>
+        string GetFileSourcePath(Dictionary<string, IResolvedDirectory> directories, string directoryId, string fileName, bool compressed, bool useLongName);
+    }
+}
diff --git a/src/api/wix/WixToolset.Extensibility/Services/IPreprocessHelper.cs b/src/api/wix/WixToolset.Extensibility/Services/IPreprocessHelper.cs
new file mode 100644
index 00000000..f7973ac2
--- /dev/null
+++ b/src/api/wix/WixToolset.Extensibility/Services/IPreprocessHelper.cs
@@ -0,0 +1,90 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved. Licensed under the Microsoft Reciprocal License. See LICENSE.TXT file in the project root for full license information.
+
+namespace WixToolset.Extensibility.Services
+{
+    using System.Xml.Linq;
+    using WixToolset.Extensibility.Data;
+
+    /// <summary>
+    /// Interface provided to help preprocessor extensions.
+    /// </summary>
+    public interface IPreprocessHelper
+    {
+        /// <summary>
+        /// Add a variable.
+        /// </summary>
+        /// <param name="context">The preprocess context.</param>
+        /// <param name="name">The variable name.</param>
+        /// <param name="value">The variable value.</param>
+        void AddVariable(IPreprocessContext context, string name, string value);
+
+        /// <summary>
+        /// Add a variable.
+        /// </summary>
+        /// <param name="context">The preprocess context.</param>
+        /// <param name="name">The variable name.</param>
+        /// <param name="value">The variable value.</param>
+        /// <param name="showWarning">Set to true to show variable overwrite warning.</param>
+        void AddVariable(IPreprocessContext context, string name, string value, bool showWarning);
+
+        /// <summary>
+        /// Evaluate a function.
+        /// </summary>
+        /// <param name="context">The preprocess context.</param>
+        /// <param name="function">The function expression including the prefix and name.</param>
+        /// <returns>The function value.</returns>
+        string EvaluateFunction(IPreprocessContext context, string function);
+
+        /// <summary>
+        /// Evaluate a function.
+        /// </summary>
+        /// <param name="context">The preprocess context.</param>
+        /// <param name="prefix">The function prefix.</param>
+        /// <param name="function">The function name.</param>
+        /// <param name="args">The arguments for the function.</param>
+        /// <returns>The function value or null if the function is not defined.</returns>
+        string EvaluateFunction(IPreprocessContext context, string prefix, string function, string[] args);
+
+        /// <summary>
+        /// Get the value of a variable expression like var.name.
+        /// </summary>
+        /// <param name="context">The preprocess context.</param>
+        /// <param name="variable">The variable expression including the optional prefix and name.</param>
+        /// <param name="allowMissingPrefix">true to allow the variable prefix to be missing.</param>
+        /// <returns>The variable value.</returns>
+        string GetVariableValue(IPreprocessContext context, string variable, bool allowMissingPrefix);
+
+        /// <summary>
+        /// Get the value of a variable.
+        /// </summary>
+        /// <param name="context">The preprocess context.</param>
+        /// <param name="prefix">The variable prefix.</param>
+        /// <param name="name">The variable name.</param>
+        /// <returns>The variable value or null if the variable is not set.</returns>
+        string GetVariableValue(IPreprocessContext context, string prefix, string name);
+
+        /// <summary>
+        /// Evaluate a Pragma.
+        /// </summary>
+        /// <param name="context">The preprocess context.</param>
+        /// <param name="pragmaName">The pragma's full name (&lt;prefix&gt;.&lt;pragma&gt;).</param>
+        /// <param name="args">The arguments to the pragma.</param>
+        /// <param name="parent">The parent element of the pragma.</param>
+        void PreprocessPragma(IPreprocessContext context, string pragmaName, string args, XContainer parent);
+
+        /// <summary>
+        /// Replaces parameters in the source text.
+        /// </summary>
+        /// <param name="context">The preprocess context.</param>
+        /// <param name="value">Text that may contain parameters to replace.</param>
+        /// <returns>Text after parameters have been replaced.</returns>
+        string PreprocessString(IPreprocessContext context, string value);
+
+        /// <summary>
+        /// Remove a variable.
+        /// </summary>
+        /// <param name="context">The preprocess context.</param>
+        /// <param name="name">The variable name.</param>
+        void RemoveVariable(IPreprocessContext context, string name);
+    }
+}
diff --git a/src/api/wix/WixToolset.Extensibility/Services/IVariableResolution.cs b/src/api/wix/WixToolset.Extensibility/Services/IVariableResolution.cs
new file mode 100644
index 00000000..adcec47f
--- /dev/null
+++ b/src/api/wix/WixToolset.Extensibility/Services/IVariableResolution.cs
@@ -0,0 +1,30 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved. Licensed under the Microsoft Reciprocal License. See LICENSE.TXT file in the project root for full license information.
+
+namespace WixToolset.Extensibility.Services
+{
+    /// <summary>
+    /// Result when resolving a variable.
+    /// </summary>
+    public interface IVariableResolution
+    {
+        /// <summary>
+        /// Indicates if the value contains variables that cannot be resolved yet.
+        /// </summary>
+        bool DelayedResolve { get; set; }
+
+        /// <summary>
+        /// Indicates whether a bind variables default value was used in the resolution.
+        /// </summary>
+        bool IsDefault { get; set; }
+
+        /// <summary>
+        /// Indicates whether the resolution updated the value.
+        /// </summary>
+        bool UpdatedValue { get; set; }
+
+        /// <summary>
+        /// The resolved value.
+        /// </summary>
+        string Value { get; set; }
+    }
+}
diff --git a/src/api/wix/WixToolset.Extensibility/Services/IVariableResolver.cs b/src/api/wix/WixToolset.Extensibility/Services/IVariableResolver.cs
new file mode 100644
index 00000000..285f1fd1
--- /dev/null
+++ b/src/api/wix/WixToolset.Extensibility/Services/IVariableResolver.cs
@@ -0,0 +1,48 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved. Licensed under the Microsoft Reciprocal License. See LICENSE.TXT file in the project root for full license information.
+
+namespace WixToolset.Extensibility.Services
+{
+    using WixToolset.Data;
+
+#pragma warning disable 1591 // TODO: add documentation
+    public interface IVariableResolver
+    {
+        void AddLocalization(Localization localization);
+#pragma warning restore 1591
+
+        /// <summary>
+        /// Add a variable.
+        /// </summary>
+        /// <param name="sourceLineNumber">The source line information for the value.</param>
+        /// <param name="name">The name of the variable.</param>
+        /// <param name="value">The value of the variable.</param>
+        /// <param name="overridable">Indicates whether the variable can be overridden by an existing variable.</param>
+        void AddVariable(SourceLineNumber sourceLineNumber, string name, string value, bool overridable);
+
+        /// <summary>
+        /// Resolve the wix variables in a value.
+        /// </summary>
+        /// <param name="sourceLineNumbers">The source line information for the value.</param>
+        /// <param name="value">The value to resolve.</param>
+        /// <returns>The resolved result.</returns>
+        IVariableResolution ResolveVariables(SourceLineNumber sourceLineNumbers, string value);
+
+        /// <summary>
+        /// Resolve the wix variables in a value.
+        /// </summary>
+        /// <param name="sourceLineNumbers">The source line information for the value.</param>
+        /// <param name="value">The value to resolve.</param>
+        /// <param name="errorOnUnknown">true if unknown variables should throw errors.</param>
+        /// <returns>The resolved value.</returns>
+        IVariableResolution ResolveVariables(SourceLineNumber sourceLineNumbers, string value, bool errorOnUnknown);
+
+        /// <summary>
+        /// Try to find localization information for dialog and (optional) control.
+        /// </summary>
+        /// <param name="dialog">Dialog identifier.</param>
+        /// <param name="control">Optional control identifier.</param>
+        /// <param name="localizedControl">Found localization information.</param>
+        /// <returns>True if localized control was found, otherwise false.</returns>
+        bool TryGetLocalizedControl(string dialog, string control, out LocalizedControl localizedControl);
+    }
+}
diff --git a/src/api/wix/WixToolset.Extensibility/Services/IWindowsInstallerBackendHelper.cs b/src/api/wix/WixToolset.Extensibility/Services/IWindowsInstallerBackendHelper.cs
new file mode 100644
index 00000000..81325131
--- /dev/null
+++ b/src/api/wix/WixToolset.Extensibility/Services/IWindowsInstallerBackendHelper.cs
@@ -0,0 +1,35 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved. Licensed under the Microsoft Reciprocal License. See LICENSE.TXT file in the project root for full license information.
+
+namespace WixToolset.Extensibility.Services
+{
+    using WixToolset.Data;
+    using WixToolset.Data.WindowsInstaller;
+
+    /// <summary>
+    /// Interface provided to help Windows Installer backend extensions.
+    /// </summary>
+    public interface IWindowsInstallerBackendHelper : IBackendHelper
+    {
+        /// <summary>
+        /// Creates a <see cref="Row"/> in the specified table.
+        /// </summary>
+        /// <param name="section">Parent section.</param>
+        /// <param name="symbol">Symbol with line information for the row.</param>
+        /// <param name="data">Windows Installer data.</param>
+        /// <param name="tableDefinition">Table definition for the row.</param>
+        /// <returns>Row created in the <paramref name="data"/>.</returns>
+        Row CreateRow(IntermediateSection section, IntermediateSymbol symbol, WindowsInstallerData data, TableDefinition tableDefinition);
+
+        /// <summary>
+        /// Looks up the registered <see cref="TableDefinition"/> for the given <see cref="IntermediateSymbol"/> and creates a <see cref="Row"/> in that table.
+        /// Goes sequentially through each field in the symbol and assigns the value to the column with the same index as the field.
+        /// If the symbol's Id is registered as the primary key then that is used for the first column and the column data is offset by 1.
+        /// </summary>
+        /// <param name="section">Parent section.</param>
+        /// <param name="symbol">Symbol to create the row from.</param>
+        /// <param name="data">Windows Installer data.</param>
+        /// <param name="tableDefinitions">Table definitions that have been registered with the binder.</param>
+        /// <returns>True if a row was created.</returns>
+        bool TryAddSymbolToMatchingTableDefinitions(IntermediateSection section, IntermediateSymbol symbol, WindowsInstallerData data, TableDefinitionCollection tableDefinitions);
+    }
+}
diff --git a/src/api/wix/WixToolset.Extensibility/Services/IWixBranding.cs b/src/api/wix/WixToolset.Extensibility/Services/IWixBranding.cs
new file mode 100644
index 00000000..4bac9ccd
--- /dev/null
+++ b/src/api/wix/WixToolset.Extensibility/Services/IWixBranding.cs
@@ -0,0 +1,26 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved. Licensed under the Microsoft Reciprocal License. See LICENSE.TXT file in the project root for full license information.
+
+namespace WixToolset.Extensibility.Services
+{
+    using System.Reflection;
+
+    /// <summary>
+    /// WiX branding interface.
+    /// </summary>
+    public interface IWixBranding
+    {
+        /// <summary>
+        /// Gets the value for CreatingApplication field (MSI Summary Information Stream).
+        /// </summary>
+        /// <returns>String for creating application.</returns>
+        string GetCreatingApplication();
+
+        /// <summary>
+        /// Replaces branding placeholders in original string.
+        /// </summary>
+        /// <param name="original">Original string containing placeholders to replace.</param>
+        /// <param name="assembly">Optional assembly with branding information, if not specified core branding is used.</param>
+        /// <returns></returns>
+        string ReplacePlaceholders(string original, Assembly assembly = null);
+    }
+}
diff --git a/src/api/wix/WixToolset.Extensibility/Services/IWixtoolsetCoreServiceProvider.cs b/src/api/wix/WixToolset.Extensibility/Services/IWixtoolsetCoreServiceProvider.cs
new file mode 100644
index 00000000..f5fb28fb
--- /dev/null
+++ b/src/api/wix/WixToolset.Extensibility/Services/IWixtoolsetCoreServiceProvider.cs
@@ -0,0 +1,34 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved. Licensed under the Microsoft Reciprocal License. See LICENSE.TXT file in the project root for full license information.
+
+namespace WixToolset.Extensibility.Services
+{
+    using System;
+    using System.Collections.Generic;
+
+    /// <summary>
+    /// The core of the service provider used to add services to the service provider.
+    /// </summary>
+    public interface IWixToolsetCoreServiceProvider : IServiceProvider
+    {
+        /// <summary>
+        /// Adds a service to the service locator.
+        /// </summary>
+        /// <param name="serviceType">Type of the service to add.</param>
+        /// <param name="creationFunction">
+        /// A function that creates the service. The create function is provided the service provider
+        /// itself to resolve additional services and a type dictionary that stores singleton services
+        /// the creation function can add its service to.
+        /// </param>
+        void AddService(Type serviceType, Func<IWixToolsetCoreServiceProvider, Dictionary<Type, object>, object> creationFunction);
+
+        /// <summary>
+        /// Adds a service to the service locator.
+        /// </summary>
+        /// <param name="creationFunction">
+        /// A function that creates the service. The create function is provided the service provider
+        /// itself to resolve additional services and a type dictionary that stores singleton services
+        /// the creation function can add its service to.
+        /// </param>
+        void AddService<T>(Func<IWixToolsetCoreServiceProvider, Dictionary<Type, object>, T> creationFunction) where T : class;
+    }
+}
diff --git a/src/api/wix/WixToolset.Extensibility/Services/ServiceProviderExtensions.cs b/src/api/wix/WixToolset.Extensibility/Services/ServiceProviderExtensions.cs
new file mode 100644
index 00000000..68484d09
--- /dev/null
+++ b/src/api/wix/WixToolset.Extensibility/Services/ServiceProviderExtensions.cs
@@ -0,0 +1,48 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved. Licensed under the Microsoft Reciprocal License. See LICENSE.TXT file in the project root for full license information.
+
+namespace WixToolset.Extensibility.Services
+{
+    using System;
+
+    /// <summary>
+    /// Service provider extensions.
+    /// </summary>
+    public static class ServiceProviderExtensions
+    {
+        /// <summary>
+        /// Gets a service from the service provider.
+        /// </summary>
+        /// <typeparam name="T">Type of service to get.</typeparam>
+        /// <param name="provider">Service provider.</param>
+        public static T GetService<T>(this IServiceProvider provider) where T : class
+        {
+            return provider.GetService(typeof(T)) as T;
+        }
+
+        /// <summary>
+        /// Gets a service from the service provider.
+        /// </summary>
+        /// <param name="provider">Service provider.</param>
+        /// <param name="serviceType">Type of service to get.</param>
+        /// <param name="service">Retrieved service.</param>
+        /// <returns>True if the service was found, otherwise false</returns>
+        public static bool TryGetService(this IServiceProvider provider, Type serviceType, out object service)
+        {
+            service = provider.GetService(serviceType);
+            return service != null;
+        }
+
+        /// <summary>
+        /// Gets a service from the service provider.
+        /// </summary>
+        /// <typeparam name="T">Type of service to get.</typeparam>
+        /// <param name="provider">Service provider.</param>
+        /// <param name="service">Retrieved service.</param>
+        /// <returns>True if the service was found, otherwise false</returns>
+        public static bool TryGetService<T>(this IServiceProvider provider, out T service) where T : class
+        {
+            service = provider.GetService(typeof(T)) as T;
+            return service != null;
+        }
+    }
+}
diff --git a/src/api/wix/WixToolset.Extensibility/WixToolset.Extensibility.csproj b/src/api/wix/WixToolset.Extensibility/WixToolset.Extensibility.csproj
new file mode 100644
index 00000000..8b18c0ed
--- /dev/null
+++ b/src/api/wix/WixToolset.Extensibility/WixToolset.Extensibility.csproj
@@ -0,0 +1,23 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!-- Copyright (c) .NET Foundation and contributors. All rights reserved. Licensed under the Microsoft Reciprocal License. See LICENSE.TXT file in the project root for full license information. -->
+
+<Project Sdk="Microsoft.NET.Sdk">
+  <PropertyGroup>
+    <TargetFrameworks>netstandard2.0</TargetFrameworks>
+    <TargetFrameworks Condition=" '$(Configuration)'=='Release' ">$(TargetFrameworks);net461;net472</TargetFrameworks>
+    <Title>WiX Toolset Extensibility</Title>
+    <Description></Description>
+    <DebugType>embedded</DebugType>
+    <PublishRepositoryUrl>true</PublishRepositoryUrl>
+    <CreateDocumentationFile>true</CreateDocumentationFile>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <PackageReference Include="WixToolset.Data" Version="4.0.*" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <PackageReference Include="Microsoft.SourceLink.GitHub" Version="1.0.0" PrivateAssets="All" />
+    <PackageReference Include="Nerdbank.GitVersioning" Version="3.3.37" PrivateAssets="all" />
+  </ItemGroup>
+</Project>
diff --git a/src/api/wix/WixToolset.Extensibility/WixToolset.Extensibility.v3.ncrunchproject b/src/api/wix/WixToolset.Extensibility/WixToolset.Extensibility.v3.ncrunchproject
new file mode 100644
index 00000000..c6001ebe
--- /dev/null
+++ b/src/api/wix/WixToolset.Extensibility/WixToolset.Extensibility.v3.ncrunchproject
@@ -0,0 +1,7 @@
+<ProjectConfiguration>
+  <Settings>
+    <AdditionalFilesToIncludeForProject>
+      <Value>..\..\version.json</Value>
+    </AdditionalFilesToIncludeForProject>
+  </Settings>
+</ProjectConfiguration>
\ No newline at end of file
diff --git a/src/api/wix/appveyor-Extensibility.cmd b/src/api/wix/appveyor-Extensibility.cmd
new file mode 100644
index 00000000..e0dfe33f
--- /dev/null
+++ b/src/api/wix/appveyor-Extensibility.cmd
@@ -0,0 +1,7 @@
+@setlocal
+@pushd %~dp0
+
+dotnet pack -c Release
+
+@popd
+@endlocal
\ No newline at end of file
diff --git a/src/api/wix/appveyor-Extensibility.yml b/src/api/wix/appveyor-Extensibility.yml
new file mode 100644
index 00000000..7c686b04
--- /dev/null
+++ b/src/api/wix/appveyor-Extensibility.yml
@@ -0,0 +1,40 @@
+# Copyright (c) .NET Foundation and contributors. All rights reserved. Licensed under the Microsoft Reciprocal License. See LICENSE.TXT file in the project root for full license information.
+#
+#  Do NOT modify this file. Update the canonical version in Home\repo-template\src\appveyor.yml
+#  then update all of the repos.
+
+branches:
+  only:
+    - master
+    - develop
+
+image: Visual Studio 2019
+
+version: 0.0.0.{build}
+configuration: Release
+
+environment:
+  DOTNET_SKIP_FIRST_TIME_EXPERIENCE: true
+  DOTNET_CLI_TELEMETRY_OPTOUT: 1
+  NUGET_XMLDOC_MODE: skip
+
+build_script:
+  - appveyor.cmd
+
+pull_requests:
+  do_not_increment_build_number: true
+
+nuget:
+  disable_publish_on_pr: true
+
+skip_branch_with_pr: true
+skip_tags: true
+
+artifacts:
+- path: build\Release\**\*.nupkg
+  name: nuget
+
+notifications:
+- provider: Slack
+  incoming_webhook:
+    secure: p5xuu+4x2JHfwGDMDe5KcG1k7gZxqYc4jWVwvyNZv5cvkubPD2waJs5yXMAXZNN7Z63/3PWHb7q4KoY/99AjauYa1nZ4c5qYqRPFRBKTHfA=
diff --git a/src/api/wix/nuget-Extensibility.config b/src/api/wix/nuget-Extensibility.config
new file mode 100644
index 00000000..6ab85be3
--- /dev/null
+++ b/src/api/wix/nuget-Extensibility.config
@@ -0,0 +1,9 @@
+<?xml version="1.0" encoding="utf-8"?>
+<configuration>
+  <packageSources>
+    <clear />
+    <add key="wixtoolset-data" value="https://ci.appveyor.com/nuget/wixtoolset-data" />
+    <add key="wixbuildtools" value="https://ci.appveyor.com/nuget/wixbuildtools" />
+    <add key="api.nuget.org" value="https://api.nuget.org/v3/index.json" protocolVersion="3" />
+  </packageSources>
+</configuration>
\ No newline at end of file