Research in Logic Programming

Unification-Free Implementation of Prolog

Paolo Frigo @ The University of Siena (Italy)

Unification is heralded as the major feature of Logic Programming, and indeed it is the prime engine of most logic languages. Nevertheless, from the execution time point of view, it is expensive and tricky. This is the reason why a restricted form of unification, iterated matching, has been introduced and studied by a number of researchers. Programs such that in every execution all the unifications can be replaced by iterated matchings are said to be unification free. We are concerned both in implementing efficiently unification free Prolog programs, and also in studying unification freedom from a theoretical point if view. In particular, our present research is focused on a program transform that maps Well Moded programs into Simply Well Moded programs, a class that shares a very appealing form of unification freedom, since it is known that the iterated matchings are actually `double' ones.

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