We beat our rules module into submission. Turns out that JBoss Rules and JavaSpaces are a pretty good match.
Towards the end of the day, we had the unit tests passing and the integration tests passing. Then it was time for the FIT tests. They busted us proper. Our co-worker Ed was pretty pumped about this. Getting busted when you think you are done by tests you wrote at the outset of a development effort is a great thing. For us, it is one less thing that we will find out when we plug in Flex to our Jini/JavaSpaces back-end. That rocks.
And our FIT tests are plugged straight into our wiki. It is h.o.t.
We also have put JBoss Rules to work with JavaSpaces. It works quite well because it is POJO based and the compiled rules can just be put into the space as Entries. If that isn't h.o.t. I don't know what is. We have a generic worker that takes Entries out of the space & reads the appropriate rules files. It just asserts the Entries directly into the rules engine (they are POJOs too - Entry is just a marker). No XML marshalling / mapping madness etc. Just objects - neat!
JBoss Rules is not as sophisticated as some commercial proprietary rules engines, but appears to be more than adequate for lots of things.