I'm trying to do a two phase commit.

Nothing beyond that -- I've heard the terminology a dozen times, and
I'm doing this purely as a technical exercise so that I can understand
how the JTA spec works in the context of a programmatic two phase
commit transaction.

I've determined that FireBird supports XA and 2PC, but I can't figure
out where the class that implements XADataSource is. I need this
class because I'm hooking into ATG Dynamo's datasource implementation,
which expects that interface.

Where is the class? I can see that there's a JCA structure, but I
don't know how to make that fit what I need. Does JayBird support XA?

Will.