Integration of Extended Unification into a Prolog Interpreter

This paper reports on the practical experiences collected during the implementation of constraint logic programming techniques via metaterms and extended unification. During the actual implementation of extended unification in a concrete PROLOG implementation some minor refinements to a specification proposed earlier [3] had to be taken care of. Further, a convention related to the interpretation of the meaning of metaterms has been moved into the specification. This paper is also thought as a supplement to the C-Prolog manual [7], describing the additional predicates and conventions for the implementation of extended unification. 1 Introduction The incorporation of semantic unification into PROLOG was inspired by the work of Kornfeld [5]. His early paper provoked some clarifications in [2]. In Kornfeld's outline a failed syntactic unification was patched by trying to prove the equality of the two terms in the extended theory. This gave rise to some problems which can be avoided altog..