--- a/graal/com.oracle.truffle.api/src/com/oracle/truffle/api/source/Source.java	Wed Mar 04 16:28:05 2015 -0800
+++ b/graal/com.oracle.truffle.api/src/com/oracle/truffle/api/source/Source.java	Wed Mar 04 16:36:27 2015 -0800
@@ -29,6 +29,8 @@
 import java.net.*;
 import java.util.*;
 
+import com.oracle.truffle.api.instrument.*;
+
 /**
  * Representation of a guest language source code unit and its contents. Sources originate in
  * several ways:
@@ -66,17 +68,28 @@
  * <li>Any access to file contents via the cache will result in a timestamp check and possible cache
  * reload.</li>
  * </ol>
+ * <p>
+ *
+ * @see SourceTag
+ * @see SourceListener
  */
 public abstract class Source {
 
     // TODO (mlvdv) consider canonicalizing and reusing SourceSection instances
     // TOOD (mlvdv) connect SourceSections into a spatial tree for fast geometric lookup
 
+    /**
+     * All Sources that have been created.
+     */
+    private static final List<WeakReference<Source>> allSources = new ArrayList<>();
+
     // Files and pseudo files are indexed.
     private static final Map<String, WeakReference<Source>> filePathToSource = new Hashtable<>();
 
     private static boolean fileCacheEnabled = true;
 
+    private static final List<SourceListener> sourceListeners = new ArrayList<>();
+
     /**
      * Gets the canonical representation of a source file, whose contents will be read lazily and
      * then cached.
@@ -106,6 +119,7 @@
         if (reset) {
             source.reset();
         }
+        notifyNewSource(source).tagAs(StandardSourceTag.FROM_FILE);
         return source;
     }
 
@@ -147,6 +161,7 @@
                 filePathToSource.put(path, new WeakReference<>(source));
             }
         }
+        notifyNewSource(source).tagAs(StandardSourceTag.FROM_FILE);
         return source;
     }
 
@@ -160,7 +175,9 @@
      */
     public static Source fromText(CharSequence chars, String description) {
         assert chars != null;
-        return new LiteralSource(description, chars.toString());
+        final LiteralSource source = new LiteralSource(description, chars.toString());
+        notifyNewSource(source).tagAs(StandardSourceTag.FROM_LITERAL);
+        return source;
     }
 
     /**
@@ -172,7 +189,9 @@
      * @throws IOException if reading fails
      */
     public static Source fromURL(URL url, String description) throws IOException {
-        return URLSource.get(url, description);
+        final URLSource source = URLSource.get(url, description);
+        notifyNewSource(source).tagAs(StandardSourceTag.FROM_URL);
+        return source;
     }
 
     /**
@@ -184,7 +203,9 @@
      * @throws IOException if reading fails
      */
     public static Source fromReader(Reader reader, String description) throws IOException {
-        return new LiteralSource(description, read(reader));
+        final LiteralSource source = new LiteralSource(description, read(reader));
+        notifyNewSource(source).tagAs(StandardSourceTag.FROM_READER);
+        return source;
     }
 
     /**
@@ -215,7 +236,9 @@
      * @return a newly created, non-indexed source representation
      */
     public static Source fromBytes(byte[] bytes, int byteIndex, int length, String description, BytesDecoder decoder) {
-        return new BytesSource(description, bytes, byteIndex, length, decoder);
+        final BytesSource source = new BytesSource(description, bytes, byteIndex, length, decoder);
+        notifyNewSource(source).tagAs(StandardSourceTag.FROM_BYTES);
+        return source;
     }
 
     /**
@@ -229,6 +252,7 @@
     public static Source asPseudoFile(CharSequence chars, String pseudoFileName) {
         final Source source = new LiteralSource(pseudoFileName, chars.toString());
         filePathToSource.put(pseudoFileName, new WeakReference<>(source));
+        notifyNewSource(source).tagAs(StandardSourceTag.FROM_LITERAL);
         return source;
     }
 
@@ -241,6 +265,48 @@
         fileCacheEnabled = enabled;
     }
 
+    /**
+     * Returns all {@link Source}s holding a particular {@link SyntaxTag}, or the whole collection
+     * of Sources if the specified tag is {@code null}.
+     *
+     * @return A collection of Sources containing the given tag.
+     */
+    public static Collection<Source> findSourcesTaggedAs(SourceTag tag) {
+        final List<Source> taggedSources = new ArrayList<>();
+        for (WeakReference<Source> ref : allSources) {
+            Source source = ref.get();
+            if (source != null) {
+                if (tag == null || source.isTaggedAs(tag)) {
+                    taggedSources.add(ref.get());
+                }
+            }
+        }
+        return taggedSources;
+    }
+
+    /**
+     * Adds a {@link SourceListener} to receive events.
+     */
+    public static void addSourceListener(SourceListener listener) {
+        assert listener != null;
+        sourceListeners.add(listener);
+    }
+
+    /**
+     * Removes a {@link SourceListener}. Ignored if listener not found.
+     */
+    public static void removeSourceListener(SourceListener listener) {
+        sourceListeners.remove(listener);
+    }
+
+    private static Source notifyNewSource(Source source) {
+        allSources.add(new WeakReference<>(source));
+        for (SourceListener listener : sourceListeners) {
+            listener.sourceCreated(source);
+        }
+        return source;
+    }
+
     private static String read(Reader reader) throws IOException {
         final BufferedReader bufferedReader = new BufferedReader(reader);
         final StringBuilder builder = new StringBuilder();
@@ -257,6 +323,8 @@
         return builder.toString();
     }
 
+    private final ArrayList<SourceTag> tags = new ArrayList<>();
+
     Source() {
     }
 
@@ -264,6 +332,32 @@
 
     protected abstract void reset();
 
+    public final boolean isTaggedAs(SourceTag tag) {
+        assert tag != null;
+        return tags.contains(tag);
+    }
+
+    public final Collection<SourceTag> getSourceTags() {
+        return Collections.unmodifiableCollection(tags);
+    }
+
+    /**
+     * Adds a {@linkplain SourceTag tag} to the set of tags associated with this {@link Source};
+     * {@code no-op} if already in the set.
+     *
+     * @return this
+     */
+    public final Source tagAs(SourceTag tag) {
+        assert tag != null;
+        if (!tags.contains(tag)) {
+            tags.add(tag);
+            for (SourceListener listener : sourceListeners) {
+                listener.sourceTaggedAs(this, tag);
+            }
+        }
+        return this;
+    }
+
     /**
      * Returns the name of this resource holding a guest language program. An example would be the
      * name of a guest language source code file.