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Temporal Concurrent Constraint Programming: Denotation, Logic and Applications
, 2002
"... The tcc model is a formalism for reactive concurrent constraint programming. We present a model of temporal concurrent constraint programming which adds to tcc the capability of modeling asynchronous and nondeterministic timed behavior. We call this tcc extension the ntcc calculus. We also give a d ..."
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Cited by 68 (24 self)
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The tcc model is a formalism for reactive concurrent constraint programming. We present a model of temporal concurrent constraint programming which adds to tcc the capability of modeling asynchronous and nondeterministic timed behavior. We call this tcc extension the ntcc calculus. We also give a denotational semantics for the strongestpostcondition of ntcc processes and, based on this semantics, we develop a proof system for lineartemporal properties of these processes. The expressiveness of ntcc is illustrated by modeling cells, timed systems such as RCX controllers, multiagent systems such as the Predator /Prey game, and musical applications such as generation of rhythms patterns and controlled improvisation. 1
Soft Concurrent Constraint Programming
, 2001
"... . Soft constraints extend classical constraints to represent multiple consistency levels, and thus provide a way to express preferences, fuzziness, and uncertainty. While there are many soft constraint solving algorithms, even distributed ones, by now there seems to be no concurrent programming fram ..."
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Cited by 50 (32 self)
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. Soft constraints extend classical constraints to represent multiple consistency levels, and thus provide a way to express preferences, fuzziness, and uncertainty. While there are many soft constraint solving algorithms, even distributed ones, by now there seems to be no concurrent programming framework where soft constraints can be handled. In this paper we show how the classical concurrent constraint (cc) programming framework can work with soft constraints, and we also propose an extension of cc languages which can use soft constraints to prune and direct the search for a solution. We believe that this new programming paradigm, called soft cc (scc), can be very useful in many webrelated scenarios. In fact, the language level allows web agents to express their interaction and negotiation protocols, and also to post their requests in terms of preferences, and the underlying soft constraint solver can nd an agreement among the agents even if their requests are incompatible. 1
Confluence in Concurrent Constraint Programming
 IN ALAGAR AND NIVAT, EDITORS, PROCEEDINGS OF AMAST '95, LNCS 936
, 1996
"... Concurrent constraint programming (ccp), like most of the concurrent paradigms, has a mechanism of global choice which makes computations dependent on the scheduling of processes. This is one of the main reasons why the formal semantics of ccp is more complicated than the one of its deterministic an ..."
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Cited by 26 (12 self)
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Concurrent constraint programming (ccp), like most of the concurrent paradigms, has a mechanism of global choice which makes computations dependent on the scheduling of processes. This is one of the main reasons why the formal semantics of ccp is more complicated than the one of its deterministic and localchoice sublanguages. In this paper we study various subsets of ccp obtained by adding some restriction on the notion of choice, or by requiring confluency, i.e. independency from the scheduling strategy. We show that it is possible to define simple denotational semantics for these subsets, for various notions of observables. Finally, as an application of our results we develop a framework for the compositional analysis of full ccp. The basic idea is to approximate an arbitrary ccp program by a program in the restricted language, and then analyze the latter, by applying the standard techniques of abstract interpretation to its denotational semantics.
Unfold/fold transformations of CCP programs
 ACM Transactions on Programming Languages and Systems
, 1998
"... We introduce a transformation system for concurrent constraint programming (CCP). We define suitable applicability conditions for the transformations which guarantee that the input/output CCP semantics is preserved also when distinguishing deadlocked computations from successful ones and when consid ..."
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Cited by 19 (5 self)
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We introduce a transformation system for concurrent constraint programming (CCP). We define suitable applicability conditions for the transformations which guarantee that the input/output CCP semantics is preserved also when distinguishing deadlocked computations from successful ones and when considering intermediate results of (possibly) nonterminating computations. The system allows us to optimize CCP programs while preserving their intended meaning: In addition to the usual benefits that one has for sequential declarative languages, the transformation of concurrent programs can also lead to the elimination of communication channels and of synchronization points, to the transformation of nondeterministic computations into deterministic ones, and to the crucial saving of computational space. Furthermore, since the transformation system preserves the deadlock behavior of programs, it can be used for proving deadlock freeness of a given program with respect to a class of queries. To this aim it is sometimes sufficient to apply our transformations and to specialize the resulting program with respect to the given queries in such a way that the obtained program is trivially deadlock free.
Nondeterminism and Infinite Computations in Constraint Programming
, 1995
"... We investigate the semantics of concurrent constraint programming and of various sublanguages, with particular emphasis on nondeterminism and infinite behavior. The aim is to find out what is the minimal structure which a domain must have in order to capture these two aspects. We show that a notion ..."
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Cited by 16 (5 self)
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We investigate the semantics of concurrent constraint programming and of various sublanguages, with particular emphasis on nondeterminism and infinite behavior. The aim is to find out what is the minimal structure which a domain must have in order to capture these two aspects. We show that a notion of observables, obtained by the upwardclosure of the results of computations, is relatively easy to model even in presence of synchronization. On the contrary modeling the exact set of results is problematic, even for the simple sublanguage of constraint logic programming. We show that most of the standard topological techniques fail in capturing this more precise notion of observables. The analysis of these failed attempts leads us to consider a categorical approach.
On the Expressive Power of Concurrent Constraint Programming Languages
 IN PPDP 2002
, 2002
"... The tcc paradigm is a formalism for timed concurrent constraint programming. Several tcc languages di#ering in their way of expressing infinite behavior have been proposed in the literature. In this paper ..."
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Cited by 15 (15 self)
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The tcc paradigm is a formalism for timed concurrent constraint programming. Several tcc languages di#ering in their way of expressing infinite behavior have been proposed in the literature. In this paper
Abstracting Synchronization in Concurrent Constraint Programming
 In Proc. 5th Int'l Symposium on Programming Language Implementation and Logic Programming
, 1994
"... ing Synchronization in Concurrent Constraint Programming ? Enea Zaffanella 1 Roberto Giacobazzi 2 Giorgio Levi 1 1 Dipartimento di Informatica, Universit`a di Pisa Corso Italia 40, 56125 Pisa (zaffanel,levi)@di.unipi.it 2 LIX, Laboratoire d'Informatique, ' Ecole Polytechnique 91128 Palaisea ..."
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Cited by 13 (5 self)
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ing Synchronization in Concurrent Constraint Programming ? Enea Zaffanella 1 Roberto Giacobazzi 2 Giorgio Levi 1 1 Dipartimento di Informatica, Universit`a di Pisa Corso Italia 40, 56125 Pisa (zaffanel,levi)@di.unipi.it 2 LIX, Laboratoire d'Informatique, ' Ecole Polytechnique 91128 Palaiseau cedex giaco@lix.polytechnique.fr Abstract. Because of synchronization based on blocking ask, some of the most important techniques for data flow analysis of (sequential) constraint logic programs (clp) are no longer applicable to cc languages. In particular, the generalized approach to the semantics, intended to factorize the (standard) semantics so as to make explicit the domaindependent features (i.e. operators and semantic objects which may be influenced by abstraction) becomes useless for relevant applications. A possible solution to this problem is based on a more abstract (nonstandard) semantics: the success semantics, which models non suspended computations only. With a program tr...
Using constraints and process algebra for specification of firstclass agent interaction protocols
 Engineering Societies in the Agents World VII, volume 4457 of LNAI
, 2007
"... Abstract. Current approaches to multiagent interaction involve specifying protocols as sets of possible interactions, and hardcoding decision mechanisms into agent programs in order to decide which path an interaction will take. This leads to several problems, three of which are particularly notab ..."
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Cited by 12 (9 self)
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Abstract. Current approaches to multiagent interaction involve specifying protocols as sets of possible interactions, and hardcoding decision mechanisms into agent programs in order to decide which path an interaction will take. This leads to several problems, three of which are particularly notable: hardcoding the decisions about interaction within an agent strongly couples the agent and the protocols it uses, which means a change to a protocol involves a changes in any agent that uses such a protocol; agents can use only the protocols that are coded into them at design time; and protocols cannot be composed at runtime to bring about more complex interactions. To achieve the full potential of multiagent systems, we believe that it is important that multiagent interaction protocols exist at runtime in systems as entities that can be inspected, referenced, composed, and shared, rather than as abstractions that emerge from the behaviour of the participants. We propose a framework, called RASA, which regards protocols as firstclass entities. In this paper, we present the first step in this framework: a formal language for specification of agent interaction protocols as firstclass entities, which, in addition to specifying the order of messages using a process algebra, also allows designers to specify the rules and consequences of protocols using constraints. In addition to allowing agents to reason about protocols at runtime in order to improve their the outcomes to better match their goals, the language allows agents to compose more complex protocols and share these at runtime. 1
Concurrent Logic/Constraint Programming: The Next 10 Years
, 1999
"... Concurrent logic/constraint programming is a simple and elegant formalism of concurrency that can potentially address a lot of important future applications including parallel, distributed, and intelligent systems. Its basic concept has been extremely stable and has allowed e#cient implementatio ..."
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Cited by 11 (7 self)
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Concurrent logic/constraint programming is a simple and elegant formalism of concurrency that can potentially address a lot of important future applications including parallel, distributed, and intelligent systems. Its basic concept has been extremely stable and has allowed e#cient implementations. However, its uniqueness makes this paradigm rather di#cult to appreciate. Many people consider concurrent logic/constraint programming to have rather little to do with the rest of logic programming. There is certainly a fundamental di#erence in the view of computation, but careful study of the di#erences will lead to the understanding and the enhancing of the whole logic programming paradigm by an analytic approach. As a model of concurrency, concurrent logic/constraint programming has its own challenges to share with other formalisms of concurrency as well. They are: (1) a counterpart of #calculus in the field of concurrency, (2) a common platform for various nonsequential forms of computing, and (3) type systems that cover both logical and physical aspects of computation.