diff -r e68342f9b906 xml.xam/src/org/netbeans/modules/xml/xam/Model.java
--- a/xml.xam/src/org/netbeans/modules/xml/xam/Model.java	Thu Mar 26 14:00:55 2009 +0300
+++ b/xml.xam/src/org/netbeans/modules/xml/xam/Model.java	Sat Apr 04 02:20:09 2009 +0400
@@ -147,6 +147,45 @@ public interface Model<C extends Compone
     boolean startTransaction();
     
     /**
+     * This method will block until a transaction can be started. A transaction
+     * in this context will fire events (such as property change) when
+     * #endTransaction() has been invoked. A transaction must be
+     * be acquired during a mutation, reading can be performed without
+     * a transaction. Only a single transaction at a time is supported. Mutations
+     * which occur based on events will not be reflected until the transaction
+     * has completed.
+     * <p>
+     * The <code>transactionDataObject</code> parameter allows passing a
+     * data object through the transaction. For example, such object can be
+     * used as a semantical source of the transaction or as a transaction's marker.
+     *
+     * @param transactionDataObject is a data object
+     * @return true if transaction is acquired successfully, else false, for example
+     * if model has transitioned into invalid state.
+     * @since 1.6
+     */
+    boolean startTransaction(Object transactionDataObject);
+
+    /**
+     * Returns the transaction's data object or null. 
+     * Null can be returned in case the data object hasn't been specified in
+     * the {@link Model#startTransaction(Object)} method or the model
+     * out of transaciton at all.
+     * <p>
+     * The transaction's data object can be not null for transactions
+     * are started implicitly (sinc, undo, redo, ...). So you should rely
+     * only on a not null value.
+     * <p>
+     * The data object can be specified only at the beginning of a transaction
+     * and can't be changed afterward. It remains alive untill transaction is
+     * ended. For example, it can be inquired when model's events are processed.
+     *
+     * @return the data object.
+     * @since 1.6
+     */
+    Object getTransactionDataObject();
+
+    /**
      * This method stops the transaction and causes all events to be fired. 
      * After all events have been fired, the document representation will be 
      * modified to reflect the current value of the model (flush). 


diff -r e68342f9b906 xml.xam/test/unit/src/org/netbeans/modules/xml/xam/AbstractModelTest.java
--- a/xml.xam/test/unit/src/org/netbeans/modules/xml/xam/AbstractModelTest.java	Thu Mar 26 14:00:55 2009 +0300
+++ b/xml.xam/test/unit/src/org/netbeans/modules/xml/xam/AbstractModelTest.java	Sat Apr 04 02:20:09 2009 +0400
@@ -212,4 +212,35 @@ public class AbstractModelTest extends T
                 "resources/test1.xml"));
         plistener.assertEvent(TestModel2.factory().MODEL_LOADED_PROPERTY, null, m);
     }
+
+    /**
+     * Tests that only one Model.MODEL_CHANGED_PROPERTY comes
+     * when a model is changed through the API.
+     * @throws java.lang.Exception
+     */
+    public void testTransactionDataObjectPassThrough() throws Exception {
+
+        final Object tDO = new Object();
+
+        model.addPropertyChangeListener(new PropertyChangeListener() {
+            public void propertyChange(PropertyChangeEvent evt) {
+                //
+                // Test the transaction's data object pass through
+                assertEquals(tDO, model.getTransactionDataObject());
+            }
+        });
+
+        model.startTransaction(tDO);
+        try {
+            TestComponent r = model.getRootComponent();
+            List<TestComponent.A> children = r.getChildren(TestComponent.A.class);
+            TestComponent.A atc = children.get(2);
+            //
+            TestComponent.B b1 = new TestComponent.B(model, 1);
+            model.addChildComponent(atc, b1, -1);
+            //
+        } finally {
+            model.endTransaction();
+        }
+    }
 }


diff -r e68342f9b906 xml.schema.model/nbproject/project.xml
--- a/xml.schema.model/nbproject/project.xml	Thu Mar 26 14:00:55 2009 +0300
+++ b/xml.schema.model/nbproject/project.xml	Sat Apr 04 02:20:09 2009 +0400
@@ -52,7 +52,7 @@ made subject to such option by the copyr
                     <compile-dependency/>
                     <run-dependency>
                         <release-version>1</release-version>
-                        <specification-version>1.0</specification-version>
+                        <specification-version>1.6</specification-version>
                     </run-dependency>
                 </dependency>
                 <dependency>


diff -r e68342f9b906 xml.xam/apichanges.xml
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/xml.xam/apichanges.xml	Sat Apr 04 02:20:09 2009 +0400
@@ -0,0 +1,151 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!-- Search for CHANGEME in this document when copying and using it: -->
+<!--
+DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
+
+Copyright 1997-2009 Sun Microsystems, Inc. All rights reserved.
+
+The contents of this file are subject to the terms of either the GNU
+General Public License Version 2 only ("GPL") or the Common
+Development and Distribution License("CDDL") (collectively, the
+"License"). You may not use this file except in compliance with the
+License. You can obtain a copy of the License at
+http://www.netbeans.org/cddl-gplv2.html
+or nbbuild/licenses/CDDL-GPL-2-CP. See the License for the
+specific language governing permissions and limitations under the
+License.  When distributing the software, include this License Header
+Notice in each file and include the License file at
+nbbuild/licenses/CDDL-GPL-2-CP.  Sun designates this
+particular file as subject to the "Classpath" exception as provided
+by Sun in the GPL Version 2 section of the License file that
+accompanied this code. If applicable, add the following below the
+License Header, with the fields enclosed by brackets [] replaced by
+your own identifying information:
+"Portions Copyrighted [year] [name of copyright owner]"
+
+Contributor(s):
+
+The Original Software is NetBeans. The Initial Developer of the Original
+Software is Sun Microsystems, Inc. Portions Copyright 1997-2009 Sun
+Microsystems, Inc. All Rights Reserved.
+
+If you wish your version of this file to be governed by only the CDDL
+or only the GPL Version 2, indicate your decision by adding
+"[Contributor] elects to include this software in this distribution
+under the [CDDL or GPL Version 2] license." If you do not indicate a
+single choice of license, a recipient has the option to distribute
+your version of this file under either the CDDL, the GPL Version 2 or
+to extend the choice of license to its licensees as provided above.
+However, if you add GPL Version 2 code and therefore, elected the GPL
+Version 2 license, then the option applies only if the new code is
+made subject to such option by the copyright holder.
+-->
+<?xml-stylesheet type="text/xml" href="../nbbuild/javadoctools/apichanges.xsl"?>
+<!DOCTYPE apichanges PUBLIC "-//NetBeans//DTD API changes list 1.0//EN" "../nbbuild/javadoctools/apichanges.dtd">
+
+<!--
+
+INFO FOR PEOPLE ADDING CHANGES:
+
+Check the DTD (apichanges.dtd) for details on the syntax. You do not
+need to regenerate the HTML, as this is part of Javadoc generation; just
+change the XML. Rough syntax of a change (several parts optional):
+
+<change>
+    <api name="compiler"/>
+    <summary>Some brief description here, can use <b>XHTML</b></summary>
+    <version major="1" minor="99"/>
+    <date day="13" month="6" year="2001"/>
+    <author login="jrhacker"/>
+    <compatibility addition="yes"/>
+    <description>
+        The main description of the change here.
+        Again can use full <b>XHTML</b> as needed.
+    </description>
+    <class package="org.openide.compiler" name="DoWhatIWantCompiler"/>
+    <issue number="14309"/>
+</change>
+
+Also permitted elements: <package>, <branch>. <version> is API spec
+version, recommended for all new changes. <compatibility> should say
+if things were added/modified/deprecated/etc. and give all information
+related to upgrading old code. List affected top-level classes and
+link to issue numbers if applicable. See the DTD for more details.
+
+Changes need not be in any particular order, they are sorted in various
+ways by the stylesheet anyway.
+
+Dates are assumed to mean "on the trunk". If you *also* make the same
+change on a stabilization branch, use the <branch> tag to indicate this
+and explain why the change was made on a branch in the <description>.
+
+Please only change this file on the trunk! Rather: you can change it
+on branches if you want, but these changes will be ignored; only the
+trunk version of this file is important.
+
+Deprecations do not count as incompatible, assuming that code using the
+deprecated calls continues to see their documented behavior. But do
+specify deprecation="yes" in <compatibility>.
+
+This file is not a replacement for Javadoc: it is intended to list changes,
+not describe the complete current behavior, for which ordinary documentation
+is the proper place.
+
+-->
+
+<apichanges>
+
+    <!-- First, a list of API names you may use: -->
+    <apidefs>
+        <apidef name="org.netbeans.modules.xml.xam">Extansible Abstract Model (XAM)</apidef>
+        <!-- etc. -->
+    </apidefs>
+
+    <!-- ACTUAL CHANGES BEGIN HERE: -->
+    <changes>
+        
+        <change id="model-changes-notification">
+            <api name="org.netbeans.modules.xml.xam"/>
+            <summary>Support passing a data object through a transaction</summary>
+            <version major="1" minor="6"/>
+            <date day="3" month="4" year="2009"/>
+            <author login="supernikita"/>
+            <compatibility binary="compatible" source="compatible" addition="yes"/>
+            <description>
+                <p>
+                Two new methods are added:
+                {@link org.netbeans.modules.xml.xam.Model#startTransaction(Object)}
+                and
+                {@link org.netbeans.modules.xml.xam.Model#getTransactionDataObject}
+                They are intended to pass an object from a transaction's invocation side
+                to an event processing side.
+                </p>
+            </description>
+            <class package="org.netbeans.modules.xml.xam" name="Model"/>
+            <issue number="160765"/>
+        </change>
+
+    </changes>
+
+    <!-- Now the surrounding HTML text and document structure: -->
+
+    <htmlcontents>
+<!-- Generated from apichanges.xml -->
+    <head>
+      <title>Change History for the Extansible Abstract Model (XAM)</title>
+      <link rel="stylesheet" href="prose.css" type="text/css"/>
+    </head>
+    <body>
+
+<p class="overviewlink"><a href="@TOP@/overview-summary.html">Overview</a></p>
+
+<h1>Introduction</h1>
+
+<p>This document lists changes made to the <a href="@TOP@/overview-summary.html">Extansible Abstract Model (XAM)</a>.</p>
+      <hr/>
+      <standard-changelists module-code-name="org.netbeans.modules.xml.xam/1"/>
+      <hr/><p>@FOOTER@</p>
+    </body>
+  </htmlcontents>
+
+</apichanges>

diff -r e68342f9b906 xml.xam/nbproject/project.properties
--- a/xml.xam/nbproject/project.properties	Thu Mar 26 14:00:55 2009 +0300
+++ b/xml.xam/nbproject/project.properties	Sat Apr 04 02:20:09 2009 +0400
@@ -42,4 +42,5 @@ is.autoload=true
 is.autoload=true
 javac.source=1.5
 javadoc.arch=${basedir}/arch.xml
-spec.version.base=1.5.0
+javadoc.apichanges=${basedir}/apichanges.xml
+spec.version.base=1.6.0

diff -r e68342f9b906 xml.xam/src/org/netbeans/modules/xml/xam/AbstractModel.java
--- a/xml.xam/src/org/netbeans/modules/xml/xam/AbstractModel.java	Thu Mar 26 14:00:55 2009 +0300
+++ b/xml.xam/src/org/netbeans/modules/xml/xam/AbstractModel.java	Sat Apr 04 02:20:09 2009 +0400
@@ -254,7 +254,7 @@ public abstract class AbstractModel<T ex
             boolean syncStartedTransaction = false;
             boolean success = false;
             try {
-                startTransaction(true, false);  //start pseudo transaction for event firing
+                startTransaction(ModificationSource.SINC, true, false);  //start pseudo transaction for event firing
                 syncStartedTransaction = true;
                 setState(getAccess().sync());
                 endTransaction();
@@ -338,10 +338,15 @@ public abstract class AbstractModel<T ex
     }
 
     public boolean startTransaction() {
-        return startTransaction(false, false);
+        return startTransaction(ModificationSource.USER, false, false);
     }
     
-    private synchronized boolean startTransaction(boolean inSync, boolean inUndoRedo) {
+    public boolean startTransaction(Object transactionDataObject) {
+        return startTransaction(transactionDataObject, false, false);
+    }
+
+    private synchronized boolean startTransaction(Object transactionDataObject,
+            boolean inSync, boolean inUndoRedo) {
         if (transaction != null && transaction.currentThreadIsTransactionThread()) {
             throw new IllegalStateException(
             "Current thread has already started a transaction");
@@ -362,7 +367,7 @@ public abstract class AbstractModel<T ex
             return false;
         }
 
-        transaction = new Transaction();
+        transaction = new Transaction(transactionDataObject);
         transactionStarted();
         setInSync(inSync);
         setInUndoRedo(inUndoRedo);
@@ -373,7 +378,11 @@ public abstract class AbstractModel<T ex
         
         return true;
     }
-    
+
+    public synchronized Object getTransactionDataObject() {
+        return transaction == null ? null : transaction.getDataObject();
+    }
+
     public synchronized void rollbackTransaction() {
         if (transaction == null) return;  // just no-op when not in transaction
         validateWrite(); // ensures that the releasing thread really owns trnx
@@ -419,7 +428,19 @@ public abstract class AbstractModel<T ex
                     "invoking startTransaction");
         }
     }
-    
+
+    /**
+     * Contains a predefined set of standard modification sources.
+     * It is used as a transactionDataObject for implicit transactions.
+     * @see Model#getTransactionDataObject
+     */
+    private enum ModificationSource {
+        USER, // model is modified by a user
+        SINC, // model is modified from sources
+        UNDO, // model is modified as a result of Undo
+        REDO  // model is modified as a result of Redo
+    }
+
     private class Transaction {
         private final List<PropertyChangeEvent> propertyChangeEvents;
         private final List<ComponentEvent> componentListenerEvents;
@@ -427,8 +448,10 @@ public abstract class AbstractModel<T ex
         private boolean eventAdded;
         private Boolean eventsAddedAfterFiring;
         private boolean hasEvents;
+        private final Object mDataObject;
         
-        public Transaction() {
+        public Transaction(Object dataObject) {
+            mDataObject = dataObject;
             propertyChangeEvents = new ArrayList<PropertyChangeEvent>();
             componentListenerEvents = new ArrayList<ComponentEvent>();
             transactionThread = Thread.currentThread();
@@ -436,7 +459,11 @@ public abstract class AbstractModel<T ex
             eventsAddedAfterFiring = null;
             hasEvents = false;
         }
-        
+
+        public Object getDataObject() {
+            return mDataObject;
+        }
+
         public void addPropertyChangeEvent(PropertyChangeEvent pce) {
             propertyChangeEvents.add(pce);
             // do not chain events during undo/redo
@@ -558,7 +585,7 @@ public abstract class AbstractModel<T ex
             boolean redoStartedTransaction = false;
             boolean needsRefresh = true;
             try {
-                startTransaction(true, true); //start pseudo transaction for event firing
+                startTransaction(ModificationSource.REDO, true, true); //start pseudo transaction for event firing
                 redoStartedTransaction = true;
                 AbstractModel.this.getAccess().prepareForUndoRedo();
                 super.redo(); 
@@ -588,7 +615,7 @@ public abstract class AbstractModel<T ex
             boolean undoStartedTransaction = false;
             boolean needsRefresh = true;
             try {
-                startTransaction(true, true); //start pseudo transaction for event firing
+                startTransaction(ModificationSource.UNDO, true, true); //start pseudo transaction for event firing
                 undoStartedTransaction = true;
                 AbstractModel.this.getAccess().prepareForUndoRedo();
                 super.undo();