Rules engines are about forward chaining (fan-out of all implications) whereas prolog is backward chaining (querying an implication). CHR (constraint handling

Rules engines are about forward chaining (fan-out of all implications) whereas prolog is backward chaining (querying an implication). CHR (constraint handling rules) is a forward chaining system built into most prologs that has prolog like syntax, and so is a replacement for business rules engines. So the choice of what to use is based on that (if you want forward chaining - business rules, or CHR of prolog), if you want backward chaining (similar to SQL) then prolog. Prolog is more elegant than the business rules engines, and also has extra features (constraint programming with finite domains for example), that business rules don't have. So in short, prolog is more comprehensive and more elegant but requires more expertise, busines rules are for "untrained" people to get working with relatively quickly.