Elliotte Rusty Harold reports that the incompatibilities between Sun's JSR 172 and SAX will "make it difficult to port standard SAX code to J2ME environments."
JSR 172 has recently been published as a second proposed final draft and comments can be sent (see jsr 172 page for details).

John Cowan has proposed "RELAX NG Type Lattices, draft 0", an annotation system allowing to declare, pattern by pattern, if it is a restriction or an extension of another pattern.
Athough the author is more than succinct about the motivations and concrete applications of this proposal, one may think that it could lead to applications similar to W3C XML Schema's derivation by restriction of complex and simple types.