Has anybody tried to evaluate the different rules engines in the interests of using it in their companies' technology stack?  I've got to do some due diligence, so need to evaluate the others.

Specifically, we're looking at a dynamic data model (not OO), and so that needs to be supported in some way (which I am heavily evaluating for drools :)).  There are plenty of other criteria, but the show stoppers are:

• unable to support a dynamic data model (being able to type different structures with the same object base, and to a lesser degree being able to compose those types into other dynamic types)
  
• Lack of support (either community or commercial)
• Lack of rule management (activation and expiry dates for rules)

Also high on the list are:

• DSL support
• rule composition and reuse (I don't really know much about how this this concept plays out with rules yet)
• Testing: the person creating the rules can write the tests, in the same designer
  
• Auditing and understanding how the engine got to the state it's in

So far I've found about 15-20 engines.  Hopefully most of them will fall out of the early criteria :)

Cheers

Stephen