Problem Reduction Rules (PRRs) in ERE
The user can (but need not) specify a set of problem reduction rules which specify how to rewrite a problem into a conjunction of subproblems. The Reactor uses these rules to recursively decompose the given behavioral constraint, deriving increasingly specific problem-solving strategies.
If no rules are provided by the user, the Projector can still search for a satisfactory behavior, but this search can be expensive without the guidance of a strategy.