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Strategic directions in constraint programming
- ACM Computing Surveys
, 1996
"... A constraint can be thought of intu-itively as a restriction on a space of possibilities. Mathematical constraints are precisely specifiable relations ..."
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A constraint can be thought of intu-itively as a restriction on a space of possibilities. Mathematical constraints are precisely specifiable relations
True concurrency in models of asynchronous circuit behaviour
, 1999
"... Abstract. In the study of asynchronous designs most authors use the interleaving model of concurrency when describing the behavior of a network; this is usually done for simplicity. The interleaving model assumes the behavior of an asynchronous circuit can be adequately represented by allowing only ..."
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Abstract. In the study of asynchronous designs most authors use the interleaving model of concurrency when describing the behavior of a network; this is usually done for simplicity. The interleaving model assumes the behavior of an asynchronous circuit can be adequately represented by allowing only one signal to change at a time. In contrast to this, true concurrency models allow an arbitrary number of simultaneous signal changes. It seems that little effort has been made to determine what effect the choice of model may have on the analysis of a network. In this paper, we attempt to discover the circumstances under which the assumption of single signal changes can be made without affecting the results of circuit analysis. We prove, in a formal network model, that, in the context of delay-insensitivity and semi-modularity, the single change assumption is valid. We also prove that the same is true for a different definition of delay-insensitivity, restricted to deterministic behaviors. Consequently, in these cases, the more complicated true concurrency analysis is not required.
Concurrent constraint programming: Calculi, languages and emerging applications
- In Newsletter of the ALP
, 2008
"... Abstract. Process calculi treat concurrent processes much like the λ-calculus treat computable functions. They provide a language in which the structure of terms represents the structure of processes together with an operational seman-tics to represent computational steps. Concurrent Constraint Prog ..."
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Abstract. Process calculi treat concurrent processes much like the λ-calculus treat computable functions. They provide a language in which the structure of terms represents the structure of processes together with an operational seman-tics to represent computational steps. Concurrent Constraint Programming (CCP) is a process calculus which combines the traditional operational view of process calculi with a declarative one based upon logic. This combination allows CCP to benefit from the large body of techniques of both process calculi and logic. This paper presents a (non-complete) survey of CCP based process calculi. We also show the applicability of the CCP model summarizing the main application of these calculi in different scenarios: timed and reactive systems, biological sys-tems, music interaction and analysis of security protocols 1
Constraint Programming: Strategic Directions
- CONSTRAINTS: AN INTERNATIONAL JOURNAL
, 1997
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Synchronous Languages
"... Abstract In this thesis we demonstrate that Plotkin's Structural Operational Semantics applies well to the class of synchronous languages. We provide interpretations in terms of labeled transition systems (LTSs) for the imperative language Esterel, the constraint based paradigm Timed Default Co ..."
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Abstract In this thesis we demonstrate that Plotkin's Structural Operational Semantics applies well to the class of synchronous languages. We provide interpretations in terms of labeled transition systems (LTSs) for the imperative language Esterel, the constraint based paradigm Timed Default Concurrent Constraint Programming (tdccp) and the visual formalism Statecharts. These LTS interpretations describe the behavior of programs in terms of reactions from global configurations to global configurations. We prove that from our LTSs we can recover existing operational semantics of the considered languages. We prove the property of congruence of some well know behavioral equivalences, by exploiting the format of our semantics rules when this is possible. Moreover, we give an axiomatization over Esterel and we prove that it is sound and complete modulo bisimulation. We provide also "distributed " interpretations for Esterel and tdccp. Namely, we provide semantics describing the behavior of programs in terms of reactions from distributed configurations to distributed configurations. We show that distributed interpretations may be used for improving debugging of programs, because they allow to isolate parts of programs causing the violation of given properties. Finally, we show that distributed interpretations for Esterel may be used to optimize the hardware implementation of the language, namely to remove redundant latches from circuits synthesized from programs. Acknowledgments First of all, I wish to thank my supervisor Andrea Maggiolo-Schettini. His guidance and suggestions have been essential during my PhD studies. Andrea supported me in all possible ways. Thanks go also to Adriano Peron for collaboration and friendship. I thank also my external reviewers, Luca Aceto and Rance Cleaveland, for their precious comments, that helped me to improve the thesis. I would also like to thank my roommates Chiara Bodei, Davide Marchignoli and Fabio Martinelli.
On Designing for Modularity
, 2003
"... Action systems, a state-based formalism for modeling reactive, distributed systems, provides a simple, yet powerful conceptual model for concurrency. Interleaved execution of actions gives the basic semantics to parallel execution of action systems. Trace refinement of action systems carried out wit ..."
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Action systems, a state-based formalism for modeling reactive, distributed systems, provides a simple, yet powerful conceptual model for concurrency. Interleaved execution of actions gives the basic semantics to parallel execution of action systems. Trace refinement of action systems carried out within the higherorder logic framework of refinement calculus lets us derive a correct implementation of a given specification. We revisit the execution concept of action systems and extend it with a synchronization mechanism, within the traditional model. We define a new parallel composition operator and show by means of illustrative examples that our new approach improves the modularity of a reactive system design. We also prove that trace refinement of composed action systems executing in a synchronized environment adds no extra complexity to the equivalent process, in the classical model. Also, when implementing our view in the generalized action systems model for hybrid systems, we bring in the possibility of creating more concise, still correct specifications of hybrid / real-time systems, by combining synchronization and interleaving.
Constraint Programming The Constraint Programming Working Group
, 1996
"... A constraint can intuitively be thought of as a restriction on a space of possibil-ities. Mathematical constraints are precisely speciable relations among several unknowns (or variables), each taking a value in a given domain. Constraints restrict the possible values that variables can take, represe ..."
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A constraint can intuitively be thought of as a restriction on a space of possibil-ities. Mathematical constraints are precisely speciable relations among several unknowns (or variables), each taking a value in a given domain. Constraints restrict the possible values that variables can take, representing some (partial)
