From the web site:
StAX is a standard XML processing API that allows you to stream XML data from and to your application. This StAX implementation is the standard pull parser implementation for JSR-173 specification.
http://stax.codehaus.org/
It is an alternative to the venerable SAX and is much more powerful and robust than TAX (see TAX Revisited for an upgraded version, TAX: A Tiny API for XML for the original).
EKB A comment copied from the TAX page:
DAG Just a note: actual SAX implementations also gulp the whole XML stream before processing, since are node oriented, and being the XML object always a node, this is read wholly before beginning parsing. StAX, on other end, is a pull-based parser, which is more stream oriented, and does note require to read the whole node before parsing it. I found it much better than SAX.