Unfortunately, we don't have specific version numbers for xml-apis.jar itself. So far, I've been relying on the version number of Xalan or Xerces, since those are the two projects who ship this most often. But we should get in the habit of actually having a specific xml-commons-external-x.y release that is then picked up by other projects, instead of rolling it yourself like the Xerces/Xalan folks have been doing.
One issue is TCK compatibility, which projects that support JCP APIs (like JAXP) must pass. Thus for xml-apis.jar, we have the tck-jaxp-1_2_0 branch that specifically supports this version of the JAXP spec; this is what most people should be shipping from now. In the future we'll need a new branch when there's a new TCK version. There's debate about whether or not we should put any effort into using code before TCK's are finalized we need to nail down as well, although that's a slightly separate issue. I suppose a good question to start would be: can we get a Xerces and a Xalan volunteer to help me make an xml-commons-external-x.y release that matches the code that Xerces/Xalan each shipped in their last releases? Other projects could pick this up now, and it would start the process of synchronizing releases in the future. - Shane
