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Approach and Results

In this work, the integration of

  1. relational languages (with REL as a representative) and
  2. LL (LISP light), a subset of COMMON LISP extended with PROLOG-like structures,
is presented. The extension of LL with PROLOG-like structures is necessary in order to permit both sublanguages to work on the same data types.

This integration is carried out on two levels:

The following diagram, a refinement of the diagram on page , illustrates the integration of relational languages and LL on both the source language and the abstract machine level (parts newly developed in this work are marked with *):

This approach meets all the requirements presented in the preceding section:

  1. Applications in which either the logic or the functional programming paradigm is best suited for some sub-problems can be developed in a relational language coupled with LL.
  2. Already existing programs in relational languages and LISP can be integrated without re-implementation. Since PROLOG and COMMON LISP are the predominant logic and functional programming languages, mainly subsets of these languages have been chosen.
  3. By mapping deterministic predicates into LL functions, the efficiency of relational programs can often be considerably improved (by a factor of 2-4; see appendix A). Especially, large relational applications tend to contain a huge number of deterministic predicates, as we were able to determine via some of our RELFUN programs [\protect\citeauthoryearBoley1991][\protect\citeauthoryearSintek1991].
  4. The expressiveness of relational programs can be improved by specifying new features as LL functions and using them as pseudo builtins.

Compared with more theoretically motivated approaches using a tight integration of logic and functional languages on the source and the abstract machine levels (e.g. [\protect\citeauthoryearLock1993][\protect\citeauthoryearHanus1991]), our approach has the following strong points:

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Harold Boley & Michael Sintek (