This report discusses the definition and implementation of constraint operations for CLP(FT), Prolog with universally quantified disequality constraints on finite trees. As a follow-up to [SH90], where we defined seve...
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This report discusses the definition and implementation of constraint operations for CLP(FT), Prolog with universally quantified disequality constraints on finite trees. As a follow-up to [SH90], where we defined several operations needed for the partial evaluation of CLP(FT), this report presents: a concise syntax for U-constraints, universally quantified disequality constraints;algorithms for the projection, equivalence, and semantic difference operations needed in the partial evaluation algorithm;a solved form for U-constraints, based on a solved form for existentially quantified equations, that allows the projection of a set of constraints onto a set of variables to be easily computed. The projection of a solved form set C of constraints onto a set V of variables is equal to those constraints c in C whose free variables are all contained in V;and a canonical form for sets of U-constraints that allows the equivalence operation to be easily computed. We also discuss applications of U-constraints and relation to previous work.
We suggest a method for justifying why a literal is or is notcontained in the answer set of a logic program. This methodmakes use of argumentation theory, more precisely of stableASPIC+ extensions. We describe a way t...
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A complete implementation of the negation as failure rule in a logic programming system requires that only ground negative literals are selected during the evaluation. Obviously there is the possibility to have only n...
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We define ShapeShifting programmes as interactive and reconfigurable moving image productions that adapt their content, on the fly, to suit the preferences of the viewers or engagers. They are automatically edited at ...
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An extended Petri net is used to model function-free logic programs with negation, i.e., normal logic programs. In this model, because of the presence of inhibitor arcs, the arbitrary applications of firing rules may ...
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ISBN:
(纸本)0818628308
An extended Petri net is used to model function-free logic programs with negation, i.e., normal logic programs. In this model, because of the presence of inhibitor arcs, the arbitrary applications of firing rules may cause a contradictory situation. We suggest two directions to avoid contradictions, greedy and secure applications of firing rules. We choose secure application in this paper and show that this is a direct translation of the well-founded semantics in the net model. Furthermore, we show that an unfounded set corresponds to a siphon in Petri net theory when we delete the transitions disabled by the secure application of firing rules, and that the property of siphons simplifies the computation of well-founded semantics for logic programs.
Realizability interpretations of logics are given by saying what it means for computational objects of some kind to realize, logical formulae. The computational objects in question might be drawn from an untyped unive...
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Realizability interpretations of logics are given by saying what it means for computational objects of some kind to realize, logical formulae. The computational objects in question might be drawn from an untyped universe of computation, such as a partial combinatory algebra, or they might be typed objects such as terms of a PCF-style programming language. In some instances, one can show that a particular untyped realizability interpretation matches a particular typed one, in the sense that they give the same set of realizable formulae. In this case, we have a very good fit indeed between the typed language and the untyped realizability model-we refer to this condition as (constructive) logical full abstraction., We give some examples of this situation for a variety of extensions of PCF. Of particular interest are some models that are logically fully abstract for typed languages including non-functional, features. Our results establish connections between what is computable in various programming languages, and what is true inside various realizability toposes. We consider some examples of logical formulae to illustrate these ideas, in particular their application to exact real-number computability. The present article summarizes the material I presented at the Domains IV workshop, plus a few subsequent developments;it is really an extended abstract for a projected journal paper. No proofs are included in the present version. I am grateful to Martin Escardó for many stimulating discussions, and especially for his input to the material in Sections 4.3 and 5.2. I also thank all the participants in the Domains IV workshop for their interest and encouragement. Andrej Bauer drew my attention to some over-enthusiastic claims involving uniform continuity on my Last Slide. The motivating philosophy behind this work owes much to the influence of Martin Hyland, and to my collaboration with Alex Simpson. This research was funded by the EPSRC Research Grant GR/L89532 "Notions of
This paper presents an abstract domain and an abstract unification function for type an al:ysis of logic programs with type definitions. Type information is inferred together with sharing and aliasing information. Ali...
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When modelling expert knowledge, default negation is very useful, but might lead to there being no stable models. Detecting the exact causes of the incoherence in the logic program manually can become quite cumbersome...
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To achieve efficient and good performance of logic programs a proposed parallel execution model based on MUSE which was implemented by SICS of Sweden has been developed and implemented. This model is an amalgamation o...
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To achieve efficient and good performance of logic programs a proposed parallel execution model based on MUSE which was implemented by SICS of Sweden has been developed and implemented. This model is an amalgamation of two main types of parallelism: AND-parallelism and OR-parallelism. The implementation of this model is done on a shared memory multiprocessor. Due to this model the logic program can be described by an AND/OR tree. The different branches of this tree are distributed to the available Processing Elements (PEs) during run time. Two scheduling techniques have been developed and implemented. In the first scheduler, The PEs are distributed through the AND/OR tree based on the sequential PROLOG (***-right depth first). The second scheduler is based on the static processing element allocation. Two benchmark programs have been used to assess the performance of this execution model;these are the natural language processing parser and an animal recognition expert system.
This work presents the Brisk Machine, a machine model for the implementation of functional languages. It is especially designed to be flexible and dynamic, so that it can support a uniform and efficient implementation...
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