SAX (http://www.megginson.com/SAX) is the ``Simple API for XML'' and should be learned by any XML novice first.
There exists already a Java parser for binary XML files: de.trantor.wap.
Xerlin (http://www.xerlin.org) is a validating XML editor (written in Java), which can edit validated (against a DTD) XML files If anyone wants to write an OpenDemo editor, it should be based on Xerlin because it comes with a plugin-interface ito extend the editor capabilities for any particular DTD.