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Concurrent Constraint Programming
, 1993
"... This paper presents a new and very rich class of (concurrent) programming languages, based on the notion of comput.ing with parhal information, and the concommitant notions of consistency and entailment. ’ In this framework, computation emerges from the interaction of concurrently executing agent ..."
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Cited by 442 (15 self)
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This paper presents a new and very rich class of (concurrent) programming languages, based on the notion of comput.ing with parhal information, and the concommitant notions of consistency and entailment. ’ In this framework, computation emerges from the interaction of concurrently executing agents that communicate by placing, checking and instantiating constraints on shared variables. Such a view of computation is interesting in the context of programming languages because of the ability to represent and manipulate partial information about the domain of discourse, in the context of concurrency because of the use of constraints for communication and control, and in the context of AI because of the availability of simple yet powerful mechanisms for controlling inference, and the promise that very rich representational/programming languages, sharing the same set of abstract properties, may be possible. To reflect this view of computation, [Sar89] develops the cc family of languages. We present here one member of the family, CC(.L,+) (pronounced “cc with Ask and Choose”) which provides the basic operations of blocking Ask and atomic Tell and an algebra of behaviors closed under prefixing, indeterministic choice, interleaving, and hiding, and provides a mutual recursion operator. cc(.L,t) is (intentionally!) very similar to Milner’s CCS, but for the radically different underlying concept of communication, which, in fact, pro’ The class is founded on the notion of “constraint logic programming ” [JL87,Mah87], fundamentally generalizes concurrent logic programming, and is the subject of the first author’s dissertation [Sar89], on which this paper is substantially based.
Algebraic Properties of Idempotent Substitutions
 Proc. of the 17th International Colloquium on Automata, Languages and Programming, volume 443 of Lecture Notes in Computer Science
, 1996
"... This paper presents an algebra of idempotent substitutions whose operations have many properties. We provide an algorithm to compute these operations and we show how they are related to the standard composition. The theory of Logic Programming can be rewritten in terms of these new operations. The a ..."
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Cited by 45 (3 self)
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This paper presents an algebra of idempotent substitutions whose operations have many properties. We provide an algorithm to compute these operations and we show how they are related to the standard composition. The theory of Logic Programming can be rewritten in terms of these new operations. The advantages are that both the operational and the declarative semantics of Horn Clause Logic can be formalized in a compositional way and the proofs of standard results, like the switching lemma, get easier and more intuitive. Moreover, this formalization can be naturally extended to a parallel computational model, and therefore it can be regarded as a basis for a theory of concurrent logic programming. 1 Introduction. A nice aspects of logic programming [1], [18] is to be based on a rigorous mathematical theory: the Horn Clause Logic (HCL). A critical aspects is that this mathematical framework makes an extensive use of the notion of substitution. The standard operational semantics of HCL [2...
Continuation Semantics for Prolog with Cut
, 1989
"... We present a denotational continuation semantics for Prolog with cut. First a uniform language B is studied, which captures the control flow aspects of Prolog. The denotational semantics for B is proven equivalent to a transition system based operational semantics. The congruence proof relies on the ..."
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Cited by 34 (5 self)
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We present a denotational continuation semantics for Prolog with cut. First a uniform language B is studied, which captures the control flow aspects of Prolog. The denotational semantics for B is proven equivalent to a transition system based operational semantics. The congruence proof relies on the representation of the operational semantics as a chain of approximations and on a convenient induction principle. Finally, we interpret the abstract language B such that we obtain equivalent denotational and operational models for Prolog itself. Section 1 Introduction In the nice textbook of Lloyd [Ll] the cut, available in all Prologsystems, is described as a controversial control facility. The cut, added to the Horn clause logic for efficiency reasons, affects the completeness of the refutation procedure. Therefore the standard declarative semantics using Herbrand models does not adequately capture the computational aspects of the Prologlanguage. In the present paper we study the Prolog...
From Concurrent Logic Programming to Concurrent Constraint Programming
 Programming, in: Advances in Logic Programming Theory
, 1993
"... The endeavor to extend logic programming to a language suitable for concurrent systems has stimulated in the last decade an intensive research, resulting in a large variety of proposals. A common feature of the various approaches is the attempt to define mechanisms for concurrency within the logical ..."
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Cited by 9 (0 self)
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The endeavor to extend logic programming to a language suitable for concurrent systems has stimulated in the last decade an intensive research, resulting in a large variety of proposals. A common feature of the various approaches is the attempt to define mechanisms for concurrency within the logical paradigm, the driving ideal being the balance between expressiveness and declarative reading. In this survey we present the motivations, the principal lines along which the field has developed, the various paradigms which have been proposed, and the main approaches to the semantic foundations. 1 Introduction Among the various reasons which have contributed to the popularity of logic programming, one is the opinion that it is an inherently parallel language, therefore suitable for parallel and distributed architectures. The pure language can already be regarded as a model for parallel computation: in the socalled process interpretation (van Emden and de Lucena 1982; Shapiro 1983), the goal...
Retractions in Comparing Prolog Semantics
 IN PROC. COMPUTING SCIENCE IN THE NETHERLANDS, PART 1, P.M.G. APERS
, 1989
"... We present an operational model O and a continuation based denotational model D for a uniform variant of Prolog, including the cut operator. The two semantical definitions make use of higher order transformations F and Y, respectively. We prove O and D equivalent in a novel way by comparing yet anot ..."
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Cited by 2 (1 self)
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We present an operational model O and a continuation based denotational model D for a uniform variant of Prolog, including the cut operator. The two semantical definitions make use of higher order transformations F and Y, respectively. We prove O and D equivalent in a novel way by comparing yet another pair of higher order transformations F and Y , that yield F and Y, respectively, by application of a suitable abstraction operator.
Transition System Specifications in Stalk Format With Bisimulation as a Congruence
 in Proceedings 11th Symposium on Theoretical Aspects of Computer Science
, 1994
"... A manysorted variant, called stalk format, of the single sorted tyftformat for transition system specifications, introduced by Groote and Vaandrager, is proposed. The stalk format is shown to be a convenient formalism to express continuationstyle transition systems for languages incorporating con ..."
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Cited by 1 (0 self)
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A manysorted variant, called stalk format, of the single sorted tyftformat for transition system specifications, introduced by Groote and Vaandrager, is proposed. The stalk format is shown to be a convenient formalism to express continuationstyle transition systems for languages incorporating concepts as, e.g., process creation or backtracking, for which the existing formats seem less adequate. It is proved, extending a similar result for the single sorted case, that for an appropriate generalization of (strong) bisimilarity for the present manysorted setting, bisimulation with respect to a transition system specification in stalk format, is a congruence. It is argued that the several conditions, required for the type of transition system specification put forward in the paper, can not be relaxed without loosing this congruence. Finally, the present format is compared with several existing ones in the literature, viz. De Simone, GSOS and pure tyftformat. Keywords and phrases se...
Retractions in Comparing Prolog Semantics
, 1990
"... We present an operational model O and a continuation based denotational model D for a uniform variant of Prolog, including the cut operator. The two semantical definitions make use of higher order transformations F and Y, respectively. We prove O and D equivalent in a novel way by comparing yet anot ..."
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We present an operational model O and a continuation based denotational model D for a uniform variant of Prolog, including the cut operator. The two semantical definitions make use of higher order transformations F and Y, respectively. We prove O and D equivalent in a novel way by comparing yet another pair of higher order transformations F and Y , that yield F and Y, respectively, by application of a suitable abstraction operator. Section 1 Introduction In [BV] we presented both an operational and a denotational continuation based semantics for the core of Prolog, and we proved these two semantics equivalent. We used a two step approach, by first deriving these results for an intermediate language, obtained by stripping the logic programming aspects (substitutions, most general unifiers and all that) from Prolog. This resulted in the abstract language B in which only the control structure from Prolog remained, such as the backtrack mechanism and the cut operator. After having co...
Continuation Semantics for Prolog with Cut
, 1989
"... We present a denotational continuation semantics for Prolog with cut. First a uniform language B is studied, which captures the control flow aspects of Prolog. The denotational semantics for B is proven equivalent to a transition system based operational semantics. The congruence proof relies on the ..."
Abstract
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We present a denotational continuation semantics for Prolog with cut. First a uniform language B is studied, which captures the control flow aspects of Prolog. The denotational semantics for B is proven equivalent to a transition system based operational semantics. The congruence proof relies on the representation of the operational semantics as a chain of approximations and on a convenient induction principle. Finally, we interpret the abstract language B such that we obtain equivalent denotational and operational models for Prolog itself. Section 1 Introduction In the nice textbook of Lloyd [Ll] the cut, available in all Prologsystems, is described as a controversial control facility. The cut, added to the Horn clause logic for efficiency reasons, affects the completeness of the refutation procedure. Therefore the standard declarative semantics using Herbrand models does not adequately capture the computational aspects of the Prologlanguage. In the present paper we study the Prolog...
Structured Operational Semantics and . . .
, 1992
"... In this paper we are interested in general properties of classes of transition system specifications in Plotkin style. The discussion takes place in a setting of labelled transition systems. The states of the transition systems are terms generated by a single sorted signature and the transitions bet ..."
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In this paper we are interested in general properties of classes of transition system specifications in Plotkin style. The discussion takes place in a setting of labelled transition systems. The states of the transition systems are terms generated by a single sorted signature and the transitions between states are defined by conditional rules over tne syntax. It is argued that in this setting it is natural to require that strong bisimulation equivalence be a congruence on the states of the transition systems. A general format, called the fyft/tyxt format, is presented for the rules in a transition system specification, such that bisimulation is always a congruence when all the rules fit this format. With a series of examples it is demonstrated that the f.vft/tyxf format cannot be generalized in any obvious way. Another series of examples illustrates the usefulness of our congruence theorem. BriefIy we touch upon the issue of modularity of transition system specifications. It is argued that certain pathological fyfi/ryxt rules (the ones which are not pure) can be disqualified because they behave badly with respect to modularization. Next we address the issue of full abstraction. We characterize the completed trace congruence induced by the operators in pure t~$/fyxf format as 2nested simulation equivalence. The pure fyj”f/fysf format includes the format given by de Simone (Theoref. Compuf. Sci. 37, 2455267 (1985)) but is incomparable to the GSOS format of Bloom, Istrail, and