General
X4O is not a language but a framework to create other XML language implementations.
X4O has an BSD style licence, to be compatible with wide range of software.
X4O can write all parsing steps in xml debug output file.
To setup set the following properties before parsing a document.
TestParser parser = new TestParser(); parser.setProperty(X4OLanguagePropertyKeys.DEBUG_OUTPUT_STREAM, new FileOutputStream(debugFile)); parser.setProperty(X4OLanguagePropertyKeys.DEBUG_OUTPUT_ELD_PARSER, true); // optional
No, X4O had no built in xslt support.
But you can implement an transforming language yourself with X4O.