Implementation of the Xalan Source Tree, which is a DOM implementation that is optimized for XSLT processing and the needs of Xalan. The primary feature of the Stree is that nodes can be parsed on one thread, while they are being read on another thread. If a requested child node has not yet arrived, the reading thread will wait until the parse thread has produced the node, thrown an exception, or marked the parent as complete. Stree nodes also contain a document order index, which is used in conjunction with the XPath module to optimize certain operations. Stree text nodes also do not build String objects until requested, and are capable of directly dispatching text events to a ContentHandler.