Results 1  10
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42
Program Derivation by Fixed Point Computation
, 1988
"... This paper develops a transformational paradigm by which nonnumerical algorithms are treated as fixed point computations derived from very high level problem specifications. We begin by presenting an abstract functional + problem specification language SQ , which is shown to express any partial re ..."
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Cited by 58 (10 self)
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This paper develops a transformational paradigm by which nonnumerical algorithms are treated as fixed point computations derived from very high level problem specifications. We begin by presenting an abstract functional + problem specification language SQ , which is shown to express any partial recursive function in a fixed point normal form. Next, we give a nondeterministic iterative schema that in the case of finite iteration generalizes the 'chaotic iteration' of Cousot and Cousot for computing fixed points of monotone functions efficiently. New techniques are discussed for recomputing fixed points of distributive functions efficiently. Numerous examples illustrate how these techniques for computing and recomputing fixed points can be incorporated within a transformational programming methodology to facilitate the design and verification of nonnumerical algorithms. 1. Introduction In a recent survey article [25] Martin Feather has said that the current state of the art of program...
Essential Concepts of Algebraic Specification and Program Development
, 1996
"... The main ideas underlying work on the modeltheoretic foundations of algebraic specification and formal program development are presented in an informal way. An attempt is made to offer an overall view, rather than new results, and to focus on the basic motivation behind the technicalities presente ..."
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Cited by 55 (15 self)
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The main ideas underlying work on the modeltheoretic foundations of algebraic specification and formal program development are presented in an informal way. An attempt is made to offer an overall view, rather than new results, and to focus on the basic motivation behind the technicalities presented elsewhere.
Mechanical Translation of Set Theoretic Problem Specifications Into Efficient RAM Code  A Case Study
 Proc. EUROCAL 85
, 1985
"... This paper illustrates a fully automatic topdown approach to program development in which formal problem specifications are mechanically translated into efficient RAM code. This code is guaranteed to be totally correct and an upper bound on its worst case asymptotic running time is automatically de ..."
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Cited by 26 (8 self)
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This paper illustrates a fully automatic topdown approach to program development in which formal problem specifications are mechanically translated into efficient RAM code. This code is guaranteed to be totally correct and an upper bound on its worst case asymptotic running time is automatically determined. The user is only required to supply the system with a formal problem specification, and is relieved of all responsibilities in the rest of the program development process. These results are obtained, in part, by greatly restricting the system to handle a class of determinate, set theoretic, tractable problems. The most essential transformational techniques that are used are fixed point iteration, finite differencing, and data structure selection. Rudimentary forms of these techniques have been implemented and used effectively in the RAPTS transformational programming system. This paper explains the conceptual underpinnings of our approach by considering the problem of attribute closure for relational databases and systematically deriving a program that implements a linear time solution. 1.
A Reification Calculus for ModelOriented Software Specification
 Formal Aspects of Computing
, 1990
"... Abstract. This paper presents a transformational approach to the derivation of implementations from modeloriented specifications of abstract data types. The purpose of this research is to reduce the number of formal proofs required in model refinement, which hinder software development. It is shown ..."
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Cited by 21 (11 self)
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Abstract. This paper presents a transformational approach to the derivation of implementations from modeloriented specifications of abstract data types. The purpose of this research is to reduce the number of formal proofs required in model refinement, which hinder software development. It is shown to be applicable to the transformation of models written in Metaiv (the specification language of Vdm) towards their refinement into, for example, Pascal or relational DBMSs. The approach includes the automatic synthesis of retrieve functions between models, and datatype invariants. The underlying algebraic semantics is the socalled final semantics “à la Wand”: a specification “is ” a model (heterogeneous algebra) which is the final object (up to isomorphism) in the category of all its implementations. The transformational calculus approached in this paper follows from exploring the properties of finite, recursively defined sets. This work extends the wellknown strategy of program transformation to model transformation, adding to previous work on a transformational style for operationdecomposition in METAIV. The modelcalculus is also useful for improving modeloriented specifications.
Foundations for a Practical Theory of Program Refinement and Transformation
, 1994
"... A wide spectrum language is presented, which is designed to facilitate the proof of the correctness of refinements and transformations. Two different proof methods are introduced and used to prove some fundamental transformations, including a general induction rule (Lemma 3.9) which enables transfor ..."
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Cited by 21 (14 self)
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A wide spectrum language is presented, which is designed to facilitate the proof of the correctness of refinements and transformations. Two different proof methods are introduced and used to prove some fundamental transformations, including a general induction rule (Lemma 3.9) which enables transformations of recursive and iterative programs to be proved by induction on their finite truncations. A theorem for proving the correctness of recursive implementations is presented (Theorem 3.21), which provides a method for introducing a loop, without requiring the user to provide a loop invariant. A powerful, general purpose, transformation for removing or introducing recursion is described and used in a case study (Section 5) in which we take a small, but highly complex, program and apply formal transformations in order to uncover an abstract specification of the behaviour of the program. The transformation theory supports a transformation system, called FermaT, in which the applicability conditions of each transformation (and hence the correctness of the result) are mechanically verified. These results together considerably simplify the construction of viable program transformation tools; practical consequences are briefly discussed.
Formal Methods to Aid the Evolution of Software
 International Journal of Software Engineering and Knowledge Engineering
, 1995
"... There is a vast collection of operational software systems which are vitally important to their users, yet are becoming increasingly difficult to maintain, enhance and keep up to date with rapidly changing requirements. For many of these so called legacy systems the option of throwing the system awa ..."
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Cited by 17 (5 self)
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There is a vast collection of operational software systems which are vitally important to their users, yet are becoming increasingly difficult to maintain, enhance and keep up to date with rapidly changing requirements. For many of these so called legacy systems the option of throwing the system away an rewriting it from scratch is not economically viable. Methods are therefore urgently required which enable these systems to evolve in a controlled manner. The approach described in this paper uses formal proven program transformations, which preserve or refine the semantics of a program while changing its form. These transformations are applied to restructure ans simplify the legacy systems and to extract higherlevel representations. By using an appropriate sequence of transformations, the extracted representation is guaranteed to be equivalent to the code. The method is based on a formal wide spectrum language, called WSL, with accompanying formal method. Over the last ten years we h...
The Early Search for Tractable Ways of Reasoning About Programs
 IEEE Annals of the History of Computing
, 2003
"... This paper traces the important steps in the history up to around 1990 of research on reasoning about programs. The main focus is on sequential imperative programs but some comments are made on concurrency. Initially, researchers focussed on ways of verifying that a program satisfies its specifi ..."
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Cited by 15 (2 self)
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This paper traces the important steps in the history up to around 1990 of research on reasoning about programs. The main focus is on sequential imperative programs but some comments are made on concurrency. Initially, researchers focussed on ways of verifying that a program satisfies its specification (or that two programs were equivalent). Over time it became clear that post facto verification is only practical for small programs and attention turned to verification methods which support the development of programs; for larger programs it is necessary to exploit a notation of compositionality. Coping with concurrent algorithms is much more challenging  this and other extensions are considered briefly. The main thesis of this paper is that the idea of reasoning about programs has been around since they were first written; the search has been to find tractable methods.
Program Derivation With Verified Transformations  A Case Study
, 1995
"... A program development methodology based on verified program transformations is described and illustrated through derivations of a high level bisimulation algorithm and an improved minimumstate DFA algorithm. Certain doubts that were raised about the correctness of an initial paperandpencil deriva ..."
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Cited by 13 (3 self)
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A program development methodology based on verified program transformations is described and illustrated through derivations of a high level bisimulation algorithm and an improved minimumstate DFA algorithm. Certain doubts that were raised about the correctness of an initial paperandpencil derivation of the DFA minimizationalgorithm were laid to rest by machinechecked formal proofs of the most difficult derivational steps. Although the protracted labor involved in designing and checking these proofs was almost overwhelming, the expense was somewhat offset by a successful reuse of major portions of these proofs. In particular, the DFA minimization algorithm is obtained by specializing and then extending the last step in the derivation of the high level bisimulation algorithm. Our experience suggests that a major focus of future research should be aimed towards improving the technology of machine checkable proofs  their construction, presentation, and reuse. This paper demonstrat...
Parallelization of DivideandConquer by Translation to Nested Loops
 J. Functional Programming
, 1997
"... We propose a sequence of equational transformations and specializations which turns a divideandconquer skeleton in Haskell into a parallel loop nest in C. Our initial skeleton is often viewed as general divideandconquer. The specializations impose a balanced call tree, a fixed degree of the prob ..."
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Cited by 12 (6 self)
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We propose a sequence of equational transformations and specializations which turns a divideandconquer skeleton in Haskell into a parallel loop nest in C. Our initial skeleton is often viewed as general divideandconquer. The specializations impose a balanced call tree, a fixed degree of the problem division, and elementwise operations. Our goal is to select parallel implementations of divideandconquer via a spacetime mapping, which can be determined at compile time. The correctness of our transformations is proved by equational reasoning in Haskell; recursion and iteration are handled by induction. Finally, we demonstrate the practicality of the skeleton by expressing Strassen's matrix multiplication in it.