From the XP homepage:

    XP is an XML 1.0 parser written in Java. It is fully conforming: it
    detects all non well-formed documents.

XP has the following design goals: Conformance and correctness, high
performance and a layered structure. It is currently non-validating but can
parse all external entities.

For more details, please see the XP homepage:

WWW: http://www.jclark.com/xml/xp/index.html