Allow users to implement compensation actions in case of unexpected unMatch/reMatch (especially, related to incremental compilation. See DROOLS-5028)

Some ideas:
A) ActivationUnMatchListener
https://issues.redhat.com/browse/JBRULES-3144

B) Allow annotation on rule (or unit) that says @RefireOnChange(LHS, RHS) // can be one or the other, or both.

C) Rising/Falling edges
http://blog.athico.com/2010/05/drools-language-enhancements-drools-6.html
"was not true, is true" "was true, still true", " was true, not true now"
people should actually be able to do this a special node in the rete graph.
it can be combined with branching too.