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diff --git a/src/WixToolset.Extensibility/CompilerExtension.cs b/src/WixToolset.Extensibility/CompilerExtension.cs
new file mode 100644
index 00000000..522ffcf8
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+++ b/src/WixToolset.Extensibility/CompilerExtension.cs
@@ -0,0 +1,74 @@
+// 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;
+
+    /// <summary>
+    /// Base class for creating a compiler extension.
+    /// </summary>
+    public abstract class CompilerExtension : ICompilerExtension
+    {
+        /// <summary>
+        /// Gets or sets the compiler core for the extension.
+        /// </summary>
+        /// <value>Compiler core for the extension.</value>
+        public ICompilerCore Core { get; set; }
+
+        /// <summary>
+        /// Gets the schema namespace for this extension.
+        /// </summary>
+        /// <value>Schema namespace supported by this extension.</value>
+        public XNamespace Namespace { get; protected set; }
+
+        /// <summary>
+        /// Called at the beginning of the compilation of a source file.
+        /// </summary>
+        public virtual void Initialize()
+        {
+        }
+
+        /// <summary>
+        /// Processes an attribute for the Compiler.
+        /// </summary>
+        /// <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>
+        public virtual void ParseAttribute(XElement parentElement, XAttribute attribute, IDictionary<string, string> context)
+        {
+            this.Core.UnexpectedAttribute(parentElement, attribute);
+        }
+
+        /// <summary>
+        /// Processes an element for the Compiler.
+        /// </summary>
+        /// <param name="parentElement">Parent element of element to process.</param>
+        /// <param name="element">Element to process.</param>
+        /// <param name="contextValues">Extra information about the context in which this element is being parsed.</param>
+        public virtual void ParseElement(XElement parentElement, XElement element, IDictionary<string, string> context)
+        {
+            this.Core.UnexpectedElement(parentElement, element);
+        }
+
+        /// <summary>
+        /// Processes an element for the Compiler, with the ability to supply a component keypath.
+        /// </summary>
+        /// <param name="parentElement">Parent element of element to process.</param>
+        /// <param name="element">Element to process.</param>
+        /// <param name="keyPath">Explicit key path.</param>
+        /// <param name="contextValues">Extra information about the context in which this element is being parsed.</param>
+        public virtual ComponentKeyPath ParsePossibleKeyPathElement(XElement parentElement, XElement element, IDictionary<string, string> context)
+        {
+            this.ParseElement(parentElement, element, context);
+            return null;
+        }
+
+        /// <summary>
+        /// Called at the end of the compilation of a source file.
+        /// </summary>
+        public virtual void Finish()
+        {
+        }
+    }
+}