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Synthesis And Transformation Of Logic Programs Using Unfold/Fold Proofs
 Journal of Logic Programming
, 1999
"... We present a method for proving properties of definite logic programs. This method is called unfold/fold proof method because it is based on the unfold/fold transformation rules... ..."
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Cited by 29 (11 self)
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We present a method for proving properties of definite logic programs. This method is called unfold/fold proof method because it is based on the unfold/fold transformation rules...
A parameterized unfold/fold transformation framework for definite logic programs
 In Principles and Practice of Declarative Programming (PPDP), LNCS 1702
, 1999
"... Given a program P, an unfold/fold program transformation system derives a sequence of programs P = P0, P1,:::, Pn, such that Pi+1 is derived from Pi by application of either an unfolding or a folding step. Existing unfold/fold transformation systems for definite logic programs differ from one anoth ..."
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Cited by 23 (6 self)
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Given a program P, an unfold/fold program transformation system derives a sequence of programs P = P0, P1,:::, Pn, such that Pi+1 is derived from Pi by application of either an unfolding or a folding step. Existing unfold/fold transformation systems for definite logic programs differ from one another mainly in the kind of folding transformations they permit at each step. Some allow folding using a single (possibly recursive) clause while others permit folding using multiple nonrecursive clauses. However, none allow folding using multiple recursive clauses that are drawn from some previous program in the transformation sequence. In this paper we develop a parameterized framework for unfold/fold transformations by suitably abstracting and extending the proofs of existing transformation systems. Various existing unfold/fold transformation systems can be obtained by instantiating the parameters of the framework. This framework enables us to not only understand the relative strengths and limitations of these systems but also construct new transformation systems. Specifically we present a more general transformation system that permits folding using multiple recursive clauses that can be drawn from any previous program in the transformation sequence. This new transformation system is also obtained by instantiating our parameterized framework.
Transformation Rules for Locally Stratified Constraint Logic Programs
, 2004
"... We propose a set of transformation rules for constraint logic programs with negation. We assume that every program is locally strati ed and, thus, it has a unique perfect model. We give sucient conditions which ensure that the proposed set of transformation rules preserves the perfect model of ..."
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Cited by 14 (13 self)
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We propose a set of transformation rules for constraint logic programs with negation. We assume that every program is locally strati ed and, thus, it has a unique perfect model. We give sucient conditions which ensure that the proposed set of transformation rules preserves the perfect model of the programs. Our rules extend in some respects the rules for logic programs and constraint logic programs already considered in the literature and, in particular, they include a rule for unfolding a clause with respect to a negative literal.
Beyond TamakiSato Style Unfold/Fold Transformations for Normal Logic Programs
 IN ASIAN, LNCS 1742
, 1999
"... Unfold/fold transformation systems for logic programs have been extensively investigated. Existing unfold/fold transformation systems for normal logic programs allow only TamakiSato style folding using clauses from a previous program in the transformation sequence: i.e., they fold using a singl ..."
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Cited by 11 (3 self)
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Unfold/fold transformation systems for logic programs have been extensively investigated. Existing unfold/fold transformation systems for normal logic programs allow only TamakiSato style folding using clauses from a previous program in the transformation sequence: i.e., they fold using a single, nonrecursive clause. In this paper we present a transformation system that permits folding in the presence of recursion, disjunction, as well as negation. We show that the transformations are correct with respect to various semantics of negation including the wellfounded model and stable model semantics.
Enhancing Partial Deduction via Unfold/Fold Rules
 Proc. LoPSTr '96
, 1996
"... We show that sometimes partial deduction produces poor program specializations because of its limited ability in (i) dealing with conjunctions of recursively defined predicates, (ii) combining partial evaluations of alternative computations, and (iii) taking into account unification failures. We pro ..."
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Cited by 7 (4 self)
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We show that sometimes partial deduction produces poor program specializations because of its limited ability in (i) dealing with conjunctions of recursively defined predicates, (ii) combining partial evaluations of alternative computations, and (iii) taking into account unification failures. We propose to extend the standard partial deduction technique by using versions of the definition rule and the folding rule which allow us to specialize predicates defined by disjunctions of conjunctions of goals. We also consider a case split rule to take into account unification failures. Moreover, in order to perform program specialization via partial deduction in an automatic way, we propose a transformation strategy which takes as parameters suitable substrategies for directing the application of every transformation rule. Finally, we show through two examples that our partial deduction technique is superior to standard partial deduction. The first example refers to the automatic derivation...
Specialization with Clause Splitting for Deriving Deterministic Constraint Logic Programs
 In Proc. IEEE Conference on Systems, Man and Cybernetics, Hammamet
, 2002
"... The reduction of nondeterminism can increase efficiency when specializing programs. We consider constraint logic programs and we propose a technique which by making use of a new transformation rule, called clause splitting, allows us to generate efficient, specialized programs which are deterministi ..."
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Cited by 5 (5 self)
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The reduction of nondeterminism can increase efficiency when specializing programs. We consider constraint logic programs and we propose a technique which by making use of a new transformation rule, called clause splitting, allows us to generate efficient, specialized programs which are deterministic. We have applied our technique to the specialization of pattern matching programs.
Flexible Continuations in Logic Programs via Unfold/Fold Transformations and Goal Generalization
 In Proceedings of the 2nd ACM SIGPLAN Workshop on Continuations
, 1997
"... We consider the use of continuations for deriving efficient logic programs. It is known that both in the case of functional and logic programming, the introduction of continuations is a valuable technique for transforming old programs into new, more efficient ones. However, in general, in order to d ..."
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Cited by 5 (3 self)
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We consider the use of continuations for deriving efficient logic programs. It is known that both in the case of functional and logic programming, the introduction of continuations is a valuable technique for transforming old programs into new, more efficient ones. However, in general, in order to derive programs with high levels of efficiency, one should introduce continuations according to suitable strategies. In particular, we show that it is preferable to introduce continuations in a flexible way, that is, during the process of program transformation itself, rather than at its beginning or at its end. We extend logic programs by allowing variables to range over goals, and we propose a set of transformation rules for this extended language. We propose a generalization strategy for the introduction of goal variables which may be viewed as continuations and they allow for the derivation of very efficient programs. 1 Introduction Continuationbased program transformations [22] have be...
Program Derivation = Rules + Strategies
 Computational Logic: Logic Programming and Beyond (Essays in honour of Bob Kowalski, Part I), Lecture Notes in Computer Science 2407
, 2001
"... In a seminal paper [38] Prof. Robert Kowalski advocated the paradigm Algorithm = Logic + Control which was intended to characterize program executions. Here we want to illustrate the corresponding paradigm Program Derivation = Rules + Strategies which is intended to characterize program derivations, ..."
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Cited by 4 (2 self)
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In a seminal paper [38] Prof. Robert Kowalski advocated the paradigm Algorithm = Logic + Control which was intended to characterize program executions. Here we want to illustrate the corresponding paradigm Program Derivation = Rules + Strategies which is intended to characterize program derivations, rather than executions. During program execution, the Logic component guarantees that the computed results are correct, that is, they are true facts in the intended model of the given program, while the Control component ensures that those facts are derived in an efficient way. Likewise, during program derivation, the Rules component guarantees that the derived programs are correct and the Strategies component ensures that the derived programs are efficient.
Optimization of Mercury programs
, 1998
"... The pure logic programming language Mercury is very well suited to the development of sophisticated program transformations due to its clean semantics and strong type, mode and determinism systems. We describe the design and implementation of some of the highlevel optimization passes of the Mercury ..."
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Cited by 4 (0 self)
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The pure logic programming language Mercury is very well suited to the development of sophisticated program transformations due to its clean semantics and strong type, mode and determinism systems. We describe the design and implementation of some of the highlevel optimization passes of the Mercury compiler, including deforestation, constraint propagation and type specialization. Mercury's mode system allows programmers to specify when a data structure can have only one reference. We present the implementation of an optimization pass to exploit this information to reuse dead cells or insert calls to place them on a free list. Contents 1 Introduction 1 2 Mercury 1 2.1 Superhomogeneous form : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 2 2.2 Quantification : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 2 2.3 Type checking : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 2 2.4 Mode analysis : : : : : : : : :...
A System for Transforming Logic Programs
, 1997
"... We describe a system for transforming logic programs using the unfold/fold methodology. The system provides the user with some predefined transformation rules. A transformation process consists of a sequence of applications of those rules, starting from a given initial program. The user selects a tr ..."
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Cited by 4 (3 self)
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We describe a system for transforming logic programs using the unfold/fold methodology. The system provides the user with some predefined transformation rules. A transformation process consists of a sequence of applications of those rules, starting from a given initial program. The user selects a transformation rule to be applied, which transforms the initial program into a new equivalent one. Several such derivation steps may be performed interactively, until the desired program is derived. Some strategies are also available, which perform fully automatically a sequence of derivation steps for realizing specific transformations. The report is intended to describe the functionalities of the system, and it should serve as a user's manual. Contents 1 Introduction 3 2 An example transformation: The scalar product 3 3 Transformations rules 5 3.1 Rules . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 3.2 Semantics preservation . . . . . . . . . ....