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SSemantics Approach: Theory and Applications
, 1994
"... The paper is a general overview of an approach to the semantics of logic programs whose aim is finding notions of models which really capture the operational semantics, and are therefore useful for defining program equivalences and for semanticsbased program analysis. The approach leads to the intr ..."
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Cited by 126 (28 self)
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The paper is a general overview of an approach to the semantics of logic programs whose aim is finding notions of models which really capture the operational semantics, and are therefore useful for defining program equivalences and for semanticsbased program analysis. The approach leads to the introduction of extended interpretations which are more expressive than Herbrand interpretations. The semantics in terms of extended interpretations can be obtained as a result of both an operational (topdown) and a fixpoint (bottomup) construction. It can also be characterized from the modeltheoretic viewpoint, by defining a set of extended models which contains standard Herbrand models. We discuss the original construction modeling computed answer substitutions, its compositional version and various semantics modeling more concrete observables. We then show how the approach can be applied to several extensions of positive logic programs. We finally consider some applications, mainly in the area of semanticsbased program transformation and analysis.
Total Correctness by Local Improvement in the Transformation of Functional Programs
 ACM Transactions on Programming Languages and Systems
, 1996
"... ion. A common form of transformation, which is easily justified by appealing to reversibility, is abstraction. The abstraction transformation lifts some instances of subexpressions from the righthand sides of a set of definitions and replaces them with function calls for some new functions. The ab ..."
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Cited by 68 (6 self)
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ion. A common form of transformation, which is easily justified by appealing to reversibility, is abstraction. The abstraction transformation lifts some instances of subexpressions from the righthand sides of a set of definitions and replaces them with function calls for some new functions. The abstraction process can be used in conjunction with a callbyneed implementation to avoid repeated evaluation of subexpressions. A wellknown example is Hughes' supercombinator abstraction [Hughes 1982]. Another form of abstraction which is common in program transformation is syntactic generalization in which an expression e is replaced by a function call g e 1 : : : e n , where g is a new function defined by g x 1 : : : xn \Delta = e 0 , such that e j e 0 f e 1 : : : e n= x 1 : : : xn g. General statements about abstractions and their correctness are notationally rather complex. In practice we have found it is easier to appeal to a reversibility argument on a casebycase basis than...
Transformation of Logic Programs
 Handbook of Logic in Artificial Intelligence and Logic Programming
, 1998
"... Program transformation is a methodology for deriving correct and efficient programs from specifications. In this chapter, we will look at the so called 'rules + strategies' approach, and we will report on the main techniques which have been introduced in the literature for that approach, i ..."
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Cited by 40 (4 self)
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Program transformation is a methodology for deriving correct and efficient programs from specifications. In this chapter, we will look at the so called 'rules + strategies' approach, and we will report on the main techniques which have been introduced in the literature for that approach, in the case of logic programs. We will also present some examples of program transformation, and we hope that through those examples the reader may acquire some familiarity with the techniques we will describe.
Total Correctness by Local Improvement in Program Transformation
 In Proceedings of the 22nd Annual ACM SIGPLANSIGACT Symposium on Principles of Programming Languages (POPL
, 1995
"... The goal of program transformation is to improve efficiency while preserving meaning. One of the best known transformation techniques is Burstall and Darlington's unfoldfold method. Unfortunately the unfoldfold method itself guarantees neither improvement in efficiency nor totalcorrectness. ..."
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Cited by 20 (3 self)
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The goal of program transformation is to improve efficiency while preserving meaning. One of the best known transformation techniques is Burstall and Darlington's unfoldfold method. Unfortunately the unfoldfold method itself guarantees neither improvement in efficiency nor totalcorrectness. The correctness problem for unfoldfold is an instance of a strictly more general problem: transformation by locally equivalencepreserving steps does not necessarily preserve (global) equivalence. This paper presents a condition for the total correctness of transformations on recursive programs, which, for the first time, deals with higherorder functional languages (both strict and nonstrict) including lazy data structures. The main technical result is an improvement theorem which says that if the local transformation steps are guided by certain optimisation concerns (a fairly natural condition for a transformation), then correctness of the transformation follows. The improvement theorem make...
Sharing of Computations
, 1993
"... This report is a revised version of my thesis of the same title, which was accepted for the Ph.D. degree in Computer Science at University of Aarhus, Denmark, in June 1993 ..."
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Cited by 18 (3 self)
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This report is a revised version of my thesis of the same title, which was accepted for the Ph.D. degree in Computer Science at University of Aarhus, Denmark, in June 1993
Simultaneous Replacement in Normal Programs
, 1993
"... The simultaneous replacement transformation operation, is here defined and studied wrt normal programs. We give applicability conditions able to ensure the correctness of the operation wrt the set of logical consequences of the completed database. We consider separately the cases in which the underl ..."
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Cited by 13 (5 self)
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The simultaneous replacement transformation operation, is here defined and studied wrt normal programs. We give applicability conditions able to ensure the correctness of the operation wrt the set of logical consequences of the completed database. We consider separately the cases in which the underlying language is infinite and finite; in this latter case we also distinguish according to the kind of domain closure axioms adopted. As corollaries we obtain results for Fitting's and Kunen's semantics. We also show how simultaneous replacement can mimic other transformation operations such as thinning, fattening and folding, thus producing applicability conditions for them too.
The replacement operation for CCP programs
 IN PROCEEDINGS OF LOPSTR '99
, 2000
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On the Correctness of the Replacement Operation for CLP Modules
, 1996
"... In this paper we study the replacement transformation for Constraint Logic Programming modules. We define new applicability conditions that guarantee the correctness of the operation also wrt module's composition: under these conditions, the original and the transformed modules have the same ob ..."
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Cited by 4 (3 self)
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In this paper we study the replacement transformation for Constraint Logic Programming modules. We define new applicability conditions that guarantee the correctness of the operation also wrt module's composition: under these conditions, the original and the transformed modules have the same observable properties also when they are composed with other modules. The applicability conditions are not bound to a specific notion of observable. Here we consider three distinct such notions. Two are operational and are based on the computed constraints; the third is the algebraic one based on the least model. We show that our transformation method can be applied in any of these distinct contexts, thus providing a parametric approach.
Automatic Correctness Proofs for Logic Program Transformations ⋆
"... Abstract. The many approaches which have been proposed in the literature for proving the correctness of unfold/fold program transformations, consist in associating suitable wellfounded orderings with the proof trees of the atoms belonging to the least Herbrand models of the programs. In practice, t ..."
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Cited by 1 (1 self)
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Abstract. The many approaches which have been proposed in the literature for proving the correctness of unfold/fold program transformations, consist in associating suitable wellfounded orderings with the proof trees of the atoms belonging to the least Herbrand models of the programs. In practice, these orderings are given by ‘clause measures’, that is, measures associated with the clauses of the programs to be transformed. In the unfold/fold transformation systems proposed so far, clause measures are fixed in advance, independently of the transformations to be proved correct. In this paper we propose a method for the automatic generation of the clause measures which, instead, takes into account the particular program transformation at hand. During the transformation process we construct a system of linear equations and inequations whose unknowns are the clause measures to be found, and the correctness of the transformation is guaranteed by the satisfiability of that system. Through some examples we show that our method is able to establish in a fully automatic way the correctness of program transformations which, by using other methods, are proved correct at the expense of fixing sophisticated clause measures. 1