A. Bossi and N. Cocco. Programs without failures. In N. E. Fuchs, editor, LOPSTR '97, volume 1463 of LNCS, pages 28--48. Springer-Verlag, 1997.  Home/Search   Document Details and Download   Summary   Related Articles   Check

....is of crucial importance. Nevertheless, relations which are not supposed to fail are quite common. We say that a relation is not supposed to fail if when called in a correct way produces at least one answer (e.g. sort, flatten and append) The ubiquity of such predicates is con rmed by [4, 11, 5] and the fact that Mercury [14] employs a mode system which actually subsume our partitioning. A partitioning is a map from the set of predicate symbols into the set ftest; non testg. We also say that the program P is correctly partitioned wrt the query A i every time that a non test atom B is ....

....partitioning has the advantage of undercovering the lazy aspects of logic programming, which is what we want to do. Checking correctness is orthogonal to the purposes of this paper, but we should mention that it can be done either using abstract interpretation [5] or on modes and types [4, 11]. The Translation Clearly, we need to capture the fact that a predicate might succeed (returning a computed answer) or fail. To do so, we introduce the datatype Result in our Haskell programs by: data Result = Suc j Fail That is, the datatype Result has two constructors, Fail and Suc, the ....

A. Bossi and N. Cocco. Programs without failures. In R. Fuchs, editor, Proc. Seventh Workshop on Logic Program Synthesis and Transformation, volume 1463 of Lecture Notes in Computer Science, pages 28-48. Springer-Verlag, Berlin, 1998.

.... numbers, then Out is an ordered merge of In1 and In2 omerge( In2, In2) omerge(In1, In1) omerge( X In1] Y In2] X Out] X Y omerge(In1, Y In2] Out) omerge( X In1] Y In2] Y Out] X Y omerge( X In1] In2, Out) 4 If we consider the query merge([5,6,7], 4,8] Xs) merge(Xs, 1,2,5] Ys) together with the delay declaration: DELAY omerge( In1 , In2 , Out ) UNTIL (nonvar(In1) AND nonvar(In2) we obtain a network of asynchronously communicating processes, represented in Figure 1. The operational behaviour assigned by SLDG resolution reflects in ....

....[14] deals only with so called local selection rules, i.e. depth first execution strategies. Their method is not appropriate for dealing with parallel programs, since local selection rules prevent parallel execution. Therefore, their method and ours are uncomparable. Recently, Bossi and Cocco [6] proposed a notion of programs without failures in the context of Prolog program verification and transformation. Such a notion turns out to coincide with well typedness together simple modedness. However, their interest is restricted to LD resolution: delay declarations and arbitrary selection ....

A. Bossi and N. Cocco. Programs without Failures. In LOPSTR '97, Lecture Notes in Computer Science, 1997. To appear.

.... are ordered lists of numbers, then Out is an ordered merge of In1 and In2 omerge( In2, In2) omerge(In1, In1) omerge( X In1] Y In2] X Out] X Y omerge(In1, Y In2] Out) omerge( X In1] Y In2] Y Out] X Y omerge( X In1] In2, Out) 5 If we consider the query omerge([5,6,7], 4,8] Xs) omerge(Xs, 1,2,5] Ys) together with the delay declaration: DELAY omerge( In1 , In2 , Out ) UNTIL (nonvar(In1) AND nonvar(In2) we obtain a network of asynchronously communicating processes, represented in Figure 1. The operational behaviour assigned by SLDG resolution re ects in ....

....of the clause s head. The approach of Krishna Rao et al. also makes use of modes. Also, Pl umer [19] reasons on termination of GHC programs by relating GHC derivations to the leftmost selection rule, and then using the techniques proposed in [18] Programs without failures Bossi and Cocco [6] proposed a notion of programs without failures in the context of Prolog program veri cation and transformation. Such a notion turns out to coincide with well typedness together simple modedness. However, their interest is restricted to LD resolution: delay declarations and arbitrary selection ....

A. Bossi and N. Cocco. Programs without Failures. In Norbert E. Fuchs, editor, LOPSTR '97, volume 1463 of Lecture Notes in Computer Science, pages 28-48. Springer-Verlag, Berlin, 1997.

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A. Bossi and N. Cocco. Programs without Failures. In N. Fuchs, editor, Proceedings LOPSTR'97, Lecture Notes in Computer Science. Springer-Verlag, Berlin, 1997.

....Abstract. In this paper we study how to verify that a pure Prolog program has solutions for a given query. The detailed analysis of the failure success behaviour of a program is necessary when dealing with transformation and verification of pure Prolog programs. In a previous work [10] we defined the class of noFD programs and queries which are characterized statically. We proved that a noFD query cannot have finitely failing derivations in a noFD program. Now, by introducing the concept of a set of exhaustive tests, we define the larger class of successsful predicates. We ....

....: List; List; Gamma : List) where : List means input term typed as a list and Gamma : List means output term typed as a list. This well known program shows the simplest case: a program which does not produce finitely failing derivations (FDs) when correctly queried. 2 In a previous work [10] we have given a sufficient condition for ensuring that a given program and query are without failures, namely they cannot have finitely failing derivations (noFD) Basically we formalize the following two observations. Let us consider reverse (or app) it is defined for any input in the specified ....

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Bossi, A., Cocco, N.: Programs without Failures. In Fuchs, N. (ed.): Proceedings LOPSTR'97, Lecture Notes in Computer Science, vol. 1463, Springer-Verlag, Berlin (1997) 28--48

....intuitive idea is that if A is non failing, then it cannot hide any potential loops of the following atoms, hence we are allowed to move it to the right. A drawback is that the condition of being non failing is generally non computable, but for very particular classes of programs and queries [BC98] noFD programs and queries, which cannot have finitely failing LD derivations, the non failing property can be trivially guaranteed. In [BCE00] we extend this transformation system for definite programs, by using the dual reasoning: If an atom B never loops then we should be able to move it ....

A. Bossi and N. Cocco. Programs without failures. In R. Fuchs, editor, Proc. Seventh Workshop on Logic Program Synthesis and Transformation, volume 1463 of Lecture Notes in Computer Science, pages 28--48. Springer-Verlag, Berlin, 1998.

....differently from SW1, is not trivial at all to verify. In fact being non failing is a semantic requirement and in general not computable. Nevertheless, if we have more information on the initial program P 0 and on the transformation sequence, such verification becomes feasible. In fact in [BC98] we have defined the class of noFD programs and queries which cannot have finitely failing LD derivations and in [BC99] we have defined a larger class of successful programs which, for terminating noFD queries, are guaranteed to have at least one successful derivation. Often the noFD and the ....

A. Bossi and N. Cocco. Programs without Failures. In N. Fuchs, editor, Proceedings LOPSTR'97, volume 1463 of Lecture Notes in Computer Science, pages 28--48. Springer-Verlag, Berlin, 1998.

....[X jXs] arc(X, Y) path(Y, Xs) We can prune 2, since it is input subsumed by the fact 1. Hence we obtain a noFD program: 1: path(X, X] which implies that the definition of path is successful. 2 6 Conclusion We have defined the class of programs and queries without failures (noFD) [9] which have the property of not having finitely failing derivations. It can be useful both for verifying program properties and for program transformation. Such a class is very restricted but usually it is sufficient that only some of the predicates in the program are in the class. We have defined ....

A. Bossi and N. Cocco. Programs without Failures. In N. Fuchs, editor, Proceedings LOPSTR'97, Lecture Notes in Computer Science. Springer-Verlag, Berlin, 1997.

....Abstract. In this paper we study how to verify that a pure Prolog program has solutions for a given query. The detailed analysis of the failure success behaviour of a program is necessary when dealing with transformation and verification of pure Prolog programs. In a previous work [10] we define the class of noFD programs and queries which cannot have finitely failing derivations. Now by introducing the concept of a set of exhaustive tests, we define the larger class of successsful predicates. We prove that such predicates have at least a successful derivation for any noFD ....

....Ys, X jZs] app(Xs, Ys, Zs) with directional type reverse( List; Gamma : List) and app( List; List; Gamma : List) This well known program shows the simplest case: a program which does not produce finitely failing derivations (FDs) when correctly queried. 2 In a previous work [10] we have given a sufficient condition for ensuring that a given program and query are without failures, namely they cannot have finitely failing derivations (noFD) Basically we formalize the following two observations. Let us consider reverse (or app) it is defined for any input in the ....

[Article contains additional citation context not shown here]

A. Bossi and N. Cocco. Programs without Failures. In N. Fuchs, editor, Proceedings LOPSTR'97, Lecture Notes in Computer Science. Springer-Verlag, Berlin, 1997.

No context found.

A. Bossi and N. Cocco. Programs without failures. In N. E. Fuchs, editor, LOPSTR '97, volume 1463 of LNCS, pages 28--48. Springer-Verlag, 1997.

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