Verification of logic programs with delay declarations

Apt, Krzysztof R.; Luitjes, I.

doi:10.1007/3-540-60043-4_47

Cited by 33 publications

(91 citation statements)

References 11 publications

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“…Another proof can be obtained by Lemma 7.5 of (Apt 1997)). Also, having proved that p is ground in any v=p in any query, we obtain the occur-check freedom by Occur-check Freedom 1 theorem of (Apt and Luitjes 1995) (with the second position of = treated as input, and all the other argument positions as output). 8 At least one position of = must be output, hence some positions of sat cl3, sat cl5a, sat cl5, and sat cl must be output.…”

Section: On Correctness-preserving Transformationsmentioning

confidence: 99%

Logic + control: On program construction and verification

Drabent

2017

Theory and Practice of Logic Programming

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This paper presents an example of formal reasoning about the semantics of a Prolog program of practical importance (the SAT solver of Howe and King). The program is treated as a definite clause logic program with added control. The logic program is constructed by means of stepwise refinement, hand in hand with its correctness and completeness proofs. The proofs are declarative -they do not refer to any operational semantics. Each step of the logic program construction follows a systematic approach to constructing programs which are provably correct and complete. We also prove that correctness and completeness of the logic program is preserved in the final Prolog program. Additionally, we prove termination, occur-check freedom and non-floundering.Our example shows how dealing with "logic" and with "control" can be separated. Most of the proofs can be done at the "logic" level, abstracting from any operational semantics.The example employs approximate specifications; they are crucial in simplifying reasoning about logic programs. It also shows that the paradigm of semantics-preserving program transformations may be not sufficient. We suggest considering transformations which preserve correctness and completeness with respect to an approximate specification.

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Section: On Correctness-preserving Transformationsmentioning

confidence: 99%

Logic + control: On program construction and verification

Drabent

2017

Theory and Practice of Logic Programming

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“…To realise the use of one predicate in several modes, one can introduce multiple (renamed) versions of the predicate [4,5,32,55]. But it is also possible to realise multiple modes without any actual code duplication.…”

Section: Modesmentioning

confidence: 99%

“…To relate input termination to local delay termination, we introduce a notion that relates delay-safe derivations with input-consuming derivations, based on an a similar concept from [5]. Definition 10.6.…”

Section: From Strong Termination To Bounded Nondeterminismmentioning

confidence: 99%

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Characterisations of Termination in Logic Programming

Pedreschi

Ruggieri

Smaus

2004

Program Development in Computational Logic

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Abstract. The procedural interpretation of logic programs and queries is parametric to the selection rule, i.e. the rule that determines which atom is selected in each resolution step. Termination of logic programs and queries depends critically on the selection rule. In this survey, we present a unified view and comparison of seven notions of universal termination considered in the literature, and the corresponding classes of programs. For each class, we focus on a sufficient, and in most cases even necessary, declarative characterisation for determining that a program is in that class. By unifying different formalisms and making appropriate assumptions, we are able to establish a formal hierarchy between the different classes and their respective declarative characterisations.

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“…Checking whether the computation for a generic query in a program will end up in a deadlock is an undecidable yet crucial problem. In order to give it a partial solution, several techniques have been employed.Among them we should mention those based on abatract interpretation (in [6,7]), mode and type anafysis (in [1,12]) and assertions (in [25, 4] (constraint) logic programs, the literature on this subject can be divided into two main branches, On one hand, we find several methods for compile-time optimization based on abstract interpretation. These methods have been recently applied also to CLP with dynamic scheduling [10,26,9] with promising results.…”

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confidence: 99%

A transformation system for CLP with dynamic scheduling and CCP

Etalle

Gabbrielli

Marchiori

1997

Proceedings of the 1997 ACM SIGPLAN Symposium on Partial Evaluation and Semantics-Based Program Manipulation

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bstract MaurizioGabbrielli~Elena MarchioriĨ n this paper we study unfold/fold transformations for constraint logic programs (CLP) with dynamic scheduling and for concurrent constraint programming (CCP). We define suitable applicability conditions for these transformations which guarantee that the original and the transformed program have the same results of successful derivations and the same deadlock free queries.The possible applications of these results are twofold. On one hand we can use the unfold/fold system to optimize CLP and CCP programs while preserving their intended meaning and in particular without the risk of introducing deadlocks. On the other hand, unfold/fold transformations can be used for proving deadlock freeness of a class of queries in a given program: to this aim it is sufficient to apply our transformations and to specialize the resulting program with respect to the given queries in such a way that the obtained program is trivially deadlock free. As shown by several interesting examples, this yields a methodology for proving deadlock freeness which is simple and powerful at the same time. Permission to mske digital/hsrd copy of psrt or all this work for personal or clsssroom use is granted without fee provided that copies are not made or distributed for profit or commercial advantage, the copyright notice, the title of the publication and its date appear, and notice ia given that copying is by permission of ACM, Inc. To copy otherwise, to republish, to post on servers, or to redistribute to lists, requires prior specific permission and/or a fee. PEPM '97 Amsterdam, ND @ 1997 ACM 0-89791 -917-319710006.,,$3,50 In nearly all the practical CLP systems [19] the flexibility of CLP comrrutation is further enhanced bv zdlowine " a dynamic selection rule which allows the computation to dynamically delay (or suspend) the selection of an atom until its argumente are sufficiently instantiated.This dynamic scheduling is obtained by adding the so-called delay declarations next to program clauses. Delay declarations, advocated by van Emden and de Lucena [34] and introduced explicitly in logic programmingby Naiah in [27], allow one to improve the efficiency of programs, to prevent run-time errors and to enforce termination. In many CLP systems they are used also to postpone the evaluation of constraints which are "too hard" for the solver. For example, in CLP(!R) [18] non-linear arithmetic constraints are delayed until they become linear.More generally, delay declarations provide the programmer with a better control over the computation and, similarly to guards in concurrent logic languages, allow one to express some degree of synchronization, usually called coroutining, among the different processes (i.e. stoma) in a program. In this sense, even though the underlying computational model uses a different kind of non-determinism, CLP with dynamic scheduling can be considered as an intermediate language between the purely sequential CLP and the concurrent language CCP. The increased expreasiveness of t...

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Verification of logic programs with delay declarations

Cited by 33 publications

References 11 publications

Logic + control: On program construction and verification

Logic + control: On program construction and verification

Characterisations of Termination in Logic Programming

A transformation system for CLP with dynamic scheduling and CCP

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