The XPath API has been part of JAXP since version 1.3, which is part of Java SE 5.0. Yet, we've never received (or at least I haven't heard) much feedback about it or the implementation that we have in the RI. Well, that's not entirely true, I have heard a few times that the implementation is not very fast (which is true), yet not much about the API itself.
In case your not familiar with the...
