The control of polyvariance is a key issue in partial deduction of logic programs. Certainly, only finitely many specialised versions of any procedure should be generated, while, on the other hand, overly severe limitations should not be imposed. In this paper, well-founded orderings serve as a starting point for tackling this so-called "global termination" problem. Polyvariance is determined by the set of distinct "partially deduced" atoms generated during partial deduction. Avoiding ad-hoc techniques, we formulate a quite general framework where this set is represented as a tree structure. Associating weights with nodes, we define a well-founded order among such structures, thus obtaining a foundation for certified global termination of partial deduction. We include an algorithm template, concrete instances of which can be used in actual implementations, prove termination and correctness, and report on the results of some experiments. Finally, we conjecture that the proposed framewor...

This paper describes an algorithm performing an analysis and transformation of logic programs. The transformation achieves two goals: redundant functors are removed from the program, and procedures may be split into two or more specialised versions handling different cases. It can be applied to most logic programming languages, including concurrent logic programming languages, because the transformations perform no unfolding of the program; they only remove some redundant operations within the unifications. The main saving is in heap usage, though time performance may also be improved. One of the main purposes of the transformation is to “clean up ” programs generated by other methods of transformation or synthesis. The analysis is an example of an abstract interpretation, and is guaranteed to terminate. A Prolog implementation of the algorithm, illustrating some meta-programming techniques, is given and some results are reported.

The endeavor to extend logic programming to a language suitable for concurrent systems has stimulated in the last decade an intensive research, resulting in a large variety of proposals. A common feature of the various approaches is the attempt to define mechanisms for concurrency within the logical paradigm, the driving ideal being the balance between expressiveness and declarative reading. In this survey we present the motivations, the principal lines along which the field has developed, the various paradigms which have been proposed, and the main approaches to the semantic foundations. 1 Introduction Among the various reasons which have contributed to the popularity of logic programming, one is the opinion that it is an inherently parallel language, therefore suitable for parallel and distributed architectures. The pure language can already be regarded as a model for parallel computation: in the so-called process interpretation (van Emden and de Lucena 1982; Shapiro 1983), the goal...