Mr. Findbugs Bill Pugh has visited Sun and I had a chance to talk with him.

One of the things he showed me is the tools bundled in FindBugs that let you
compare two findbugs.xml and then report trend analysis, like how many are
added, how many are fixed, etc. I think it would be nice to integrate similar
functionality in the findbugs plugin. He said such correlation feature is
readily available in findbugs so we should be able to call it easily.