XMT (XStream Migration Tool) is an open source library to migrate [XStream|http://xstream.codehaus.org/] serialized XML when the associated Java class evolves. XStream is a popular library to serialize Java object to XML and back again, and XMT enables a smooth migration of this XML with the help of [dom4j|http://dom4j.sourceforge.net/] when you change class definition of the Java object.