Adding Constraints to Logic-based Formalisms

Constraints are predefined relations with a special implementation mechanism. Logic formalisms provide specific reasoning facilities. We look at the effect of adding constraints to existing logic-based executable formalisms, focussing on the semantics of the combined formalisms. We find that in cases where this has been successful the operations of the formalism can be formulated logically and then extended easily to constraints. In many cases a disjunctive property of the constraints is reflected in the combined formalism, to the detriment of efficiency. 1 Introduction Constraints are essentially relations among variables ranging over fixed domains. Since most logics incorporate predicate symbols -- which are interpreted as relations -- and variables, there is clearly a degree of compatibility between constraint- and logic-based formalisms. Indeed, in some sense both constraint programming and logic programming can be considered part of an umbrella relational programming paradigm. ..