Index: trunk/src/com/drew/metadata/MetadataReader.java
===================================================================
--- trunk/src/com/drew/metadata/MetadataReader.java	(revision 4231)
+++ trunk/src/com/drew/metadata/MetadataReader.java	(revision 6127)
@@ -1,27 +1,44 @@
 /*
- * This is public domain software - that is, you can do whatever you want
- * with it, and include it software that is licensed under the GNU or the
- * BSD license, or whatever other licence you choose, including proprietary
- * closed source licenses.  I do ask that you leave this header in tact.
+ * Copyright 2002-2012 Drew Noakes
  *
- * If you make modifications to this code that you think would benefit the
- * wider community, please send me a copy and I'll post it on my site.
+ *    Licensed under the Apache License, Version 2.0 (the "License");
+ *    you may not use this file except in compliance with the License.
+ *    You may obtain a copy of the License at
  *
- * If you make use of this code, I'd appreciate hearing about it.
- *   drew@drewnoakes.com
- * Latest version of this software kept at
- *   http://drewnoakes.com/
+ *        http://www.apache.org/licenses/LICENSE-2.0
  *
- * Created by dnoakes on 26-Nov-2002 11:21:43 using IntelliJ IDEA.
+ *    Unless required by applicable law or agreed to in writing, software
+ *    distributed under the License is distributed on an "AS IS" BASIS,
+ *    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ *    See the License for the specific language governing permissions and
+ *    limitations under the License.
+ *
+ * More information about this project is available at:
+ *
+ *    http://drewnoakes.com/code/exif/
+ *    http://code.google.com/p/metadata-extractor/
  */
 package com.drew.metadata;
 
+import com.drew.lang.BufferReader;
+import com.drew.lang.annotations.NotNull;
+
 /**
+ * Interface through which all classes responsible for decoding a particular type of metadata may be called.
+ * Note that the data source is not specified on this interface.  Instead it is suggested that implementations
+ * take their data within a constructor.  Constructors might be overloaded to allow for different sources, such as
+ * files, streams and byte arrays.  As such, instances of implementations of this interface would be single-use and
+ * not thread-safe.
  *
+ * @author Drew Noakes http://drewnoakes.com
  */
 public interface MetadataReader
 {
-    public Metadata extract();
-
-    public Metadata extract(Metadata metadata);
+    /**
+     * Extract metadata from the source and merge it into an existing Metadata object.
+     *
+     * @param reader   The reader from which the metadata should be extracted.
+     * @param metadata The Metadata object into which extracted values should be merged.
+     */
+    public void extract(@NotNull final BufferReader reader, @NotNull final Metadata metadata);
 }