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28
Foundations of Timed Concurrent Constraint Programming
 Proceedings of the Ninth Annual IEEE Symposium on Logic in Computer Science
, 1994
"... We develop a model for timed, reactive computation by extending the asynchronous, untimed concurrent constraint programming model in a simple and uniform way. In the spirit of process algebras, we develop some combinators expressible in this model, and reconcile their operational, logical and denota ..."
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Cited by 103 (10 self)
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We develop a model for timed, reactive computation by extending the asynchronous, untimed concurrent constraint programming model in a simple and uniform way. In the spirit of process algebras, we develop some combinators expressible in this model, and reconcile their operational, logical and denotational character. We show how programs may be compiled into finitestate machines with loopfree computations at each state, thus guaranteeing bounded response time. 1 Introduction and Motivation Reactive systems [12,3,9] are those that react continuously with their environment at a rate controlled by the environment. Execution in a reactive system proceeds in bursts of activity. In each phase, the environment stimulates the system with an input, obtains a response in bounded time, and may then be inactive (with respect to the system) for an arbitrary period of time before initiating the next burst. Examples of reactive systems are controllers and signalprocessing systems. The primary issu...
Timed Default Concurrent Constraint Programming
 Journal of Symbolic Computation
, 1996
"... Synchronous programming (Berry (1989)) is a powerful approach to programming reactive systems. Following the idea that "processes are relations extended over time" (Abramsky (1993)), we propose a simple but powerful model for timed, determinate computation, extending the closureoperator m ..."
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Cited by 73 (14 self)
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Synchronous programming (Berry (1989)) is a powerful approach to programming reactive systems. Following the idea that "processes are relations extended over time" (Abramsky (1993)), we propose a simple but powerful model for timed, determinate computation, extending the closureoperator model for untimed concurrent constraint programming (CCP). In (Saraswat et al. 1994a) we had proposed a model for this called tcc here we extend the model of tcc to express strong timeouts: if an event A does not happen through time t, cause event B to happen at time t. Such constructs arise naturally in practice (e.g. in modeling transistors) and are supported in synchronous programming languages. The fundamental conceptual difficulty posed by these operations is that they are nonmonotonic. We provide a compositional semantics to the nonmonotonic version of concurrent constraint programming (Default cc) obtained by changing the underlying logic from intuitionistic logic to Reiter's default logic...
Executing Reactive, Modelbased Programs through Graphbased Temporal Planning
 IN PROCEEDINGS OF IJCAI2001
, 2001
"... In the future, webs of unmanned air and space vehicles will act together to robustly perform elaborate missions in uncertain environments. We coordinate these systems by introducing a reactive modelbased programming language (RMPL) that combines within a single unified representation the flex ..."
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Cited by 65 (27 self)
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In the future, webs of unmanned air and space vehicles will act together to robustly perform elaborate missions in uncertain environments. We coordinate these systems by introducing a reactive modelbased programming language (RMPL) that combines within a single unified representation the flexibility of embedded programming and reactive execution languages, and the deliberative reasoning power of temporal planners. The KIRK planning system takes as input a problem expressed as a RMPL program, and compiles it into a temporal plan network (TPN), similar to those used by temporal planners, but extended for symbolic constraints and decisions. This intermediate representation clarifies the relation between temporal planning and causallink planning, and permits a single task model to be used for planning and execution. Such a
Programming in Timed Concurrent Constraint Languages
, 1994
"... This paper explores Lhc expressive power of Lhc tcc paradigm. The origin of Lhc work in Lhc inLcgraLion of synchronous and consLrainL programming is described. The basic conceptual and maLhcmaLical framework developed in Lhc spirk of Lhc modelbased approach characLcrisLic of LhcorcLical compuLcr sc ..."
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Cited by 33 (4 self)
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This paper explores Lhc expressive power of Lhc tcc paradigm. The origin of Lhc work in Lhc inLcgraLion of synchronous and consLrainL programming is described. The basic conceptual and maLhcmaLical framework developed in Lhc spirk of Lhc modelbased approach characLcrisLic of LhcorcLical compuLcr science is reviewed. Wc show LhaL a range of consLrucLs for expressing LimcouLs, prccmpLion and oLhcr complicaLcd paLLcrns of Lcmporal acLivky arc expressible in the basic model and languageframework. Indeed, we present a single construct on processes, definable in the language, that can simulate the effect of other preemption constructs
Stochastic processes as concurrent constraint programs
 In Symposium on Principles of Programming Languages
, 1999
"... ) Vineet Gupta Radha Jagadeesan Prakash Panangaden y vgupta@mail.arc.nasa.gov radha@cs.luc.edu prakash@cs.mcgill.ca Caelum Research Corporation Dept. of Math. and Computer Sciences School of Computer Science NASA Ames Research Center Loyola UniversityLake Shore Campus McGill University Moffe ..."
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Cited by 32 (1 self)
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) Vineet Gupta Radha Jagadeesan Prakash Panangaden y vgupta@mail.arc.nasa.gov radha@cs.luc.edu prakash@cs.mcgill.ca Caelum Research Corporation Dept. of Math. and Computer Sciences School of Computer Science NASA Ames Research Center Loyola UniversityLake Shore Campus McGill University Moffett Field CA 94035, USA Chicago IL 60626, USA Montreal, Quebec, Canada Abstract This paper describes a stochastic concurrent constraint language for the description and programming of concurrent probabilistic systems. The language can be viewed both as a calculus for describing and reasoning about stochastic processes and as an executable language for simulating stochastic processes. In this language programs encode probability distributions over (potentially infinite) sets of objects. We illustrate the subtleties that arise from the interaction of constraints, random choice and recursion. We describe operational semantics of these programs (programs are run by sampling random choices), deno...
Computing With Continuous Change
"... A central challenge in computer science and knowledge representation is the integration of conceptual frameworks for continuous and discrete change, as exemplified by the theory of differential equations and real analysis on the one hand, and the theory of programming languages on the other. We take ..."
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Cited by 28 (5 self)
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A central challenge in computer science and knowledge representation is the integration of conceptual frameworks for continuous and discrete change, as exemplified by the theory of differential equations and real analysis on the one hand, and the theory of programming languages on the other. We take the first steps towards such an integrated theory by presenting a recipe for the construction of continuous programming languages  languages in which state dynamics can be described by differential equations. The basic idea is to start with an untimed language and extend it uniformly over dense (real) time. We present a concrete mathematical model and language (the Hybrid concurrent constraint programming model, Hybrid cc) instantiating these ideas. The language is intended to be used for modeling and programming hybrid systems. The language is declarative  programs can be understood as formulas that place constraints on the (temporal) evolution of the system, with parallel compositio...
Mode Estimation of Modelbased Programs: Monitoring Systems with Complex Behavior
 in: Proceedings of IJCAI01
, 2001
"... Deductive modeestimation has become an essential component of robotic space systems, like NASA’s deep space probes. Future robots will serve as components of large robotic networks. Monitoring these networks will require modeling languages and estimators that handle the sophisticated behaviors of r ..."
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Cited by 27 (17 self)
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Deductive modeestimation has become an essential component of robotic space systems, like NASA’s deep space probes. Future robots will serve as components of large robotic networks. Monitoring these networks will require modeling languages and estimators that handle the sophisticated behaviors of robotic components. This paper introduces RMPL, a rich modeling language that combines reactive programming constructs with probabilistic, constraintbased modeling, and that offers a simple semantics in terms of hidden Markov models (HMMs). To support efficient realtime deduction, we translate RMPL models into a compact encoding of HMMs called probabilistic hierarchical constraint automata (PHCA). Finally, we use these models to track a system’s most likely states by extending traditional HMM belief update. 1
Programming in Hybrid Constraint Languages
 Hybrid Systems II, volume 999 of LNCS
, 1995
"... . We present a language, Hybrid cc, for modeling hybrid systems compositionally. This language is declarative, with programs being understood as logical formulas that place constraints upon the temporal evolution of a system. We show the expressiveness of our language by presenting several examples, ..."
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Cited by 22 (8 self)
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. We present a language, Hybrid cc, for modeling hybrid systems compositionally. This language is declarative, with programs being understood as logical formulas that place constraints upon the temporal evolution of a system. We show the expressiveness of our language by presenting several examples, including a model for the paperpath of a photocopier. We describe an interpreter for our language, and provide traces for some of the example programs. 1 Introduction and Motivation The constant marketplace demand of ever greater functionality at ever lower price is forcing the artifacts our industrial society designs to become ever more complex. Before the advent of silicon, this complexity would have been unmanageable. Now, the economics and power of digital computation make it the medium of choice for gluing together and controlling complex systems composed of electromechanical and computationally realized elements. As a result, the construction of the software to implement, monitor, c...
Modelbased monitoring and diagnosis of systems with softwareextended behavior
 In Proc. 20th National Conference on Artificial Intelligence
, 2005
"... Modelbased diagnosis has largely operated on hardware systems. However, in most complex systems today, hardware is augmented with software functions that influence the system’s behavior. In this paper, hardware models are extended to include the behavior of associated embedded software, resulting i ..."
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Cited by 14 (3 self)
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Modelbased diagnosis has largely operated on hardware systems. However, in most complex systems today, hardware is augmented with software functions that influence the system’s behavior. In this paper, hardware models are extended to include the behavior of associated embedded software, resulting in more comprehensive diagnoses. Prior work introduced probabilistic, hierarchical, constraintbased automata (PHCA) to allow the uniform and compact encoding of both hardware and software behavior. This paper focuses on PHCAbased monitoring and diagnosis to ensure the robustness of complex systems. We introduce a novel approach that frames diagnosis over a finite time horizon as a soft constraint optimization problem (COP), allowing us to leverage an extensive body of efficient solution methods for COPs. The solutions to the COP correspond to the most likely evolutions of the complex system. We demonstrate our approach on a visionbased rover navigation system, and models of the SPHERES and Earth Observing One spacecraft.
Default Timed Concurrent Constraint Programming (Extended Abstract)
, 1995
"... We extend the model of [SJG94b] to express strong timeouts (and preemption): if an event A does not happen through time t, cause event B to happen at time t. Such constructs arise naturally in practice (e.g. in modeling transistors) and are supported in languages such as Esterel (through instanta ..."
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Cited by 12 (2 self)
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We extend the model of [SJG94b] to express strong timeouts (and preemption): if an event A does not happen through time t, cause event B to happen at time t. Such constructs arise naturally in practice (e.g. in modeling transistors) and are supported in languages such as Esterel (through instantaneous watchdogs) and Lustre (through the "current" operator). The fundamental conceptual difficulty posed by these operators is that they are nonmonotonic. We provide a simple compositional semantics to the nonmonotonic version of concurrent constraint programming (CCP) obtained by changing the underlying logic from intuitionistic logic to Reiter 's default logic [Rei80]. This allows us to use the same construction (uniform extension through time) to develop Default Timed CCP (Default tcc) as we had used to develop Timed CCP (tcc) from CCP [SJG94b]. Indeed the smooth embedding of CCP processes into Default cc processes lifts to a smooth embedding of tcc processes into Default t...