Concurrency, Time and Constraints ?

Concurrency, Time and Constraints ? Frank D. ValenciaDept. of Information Technology, Uppsala UniversityBox 337 SE-751 05 Uppsala, SwedenEmail: frankv@it.uu.se Fax: +46 18 511 925Abstract Concurrent constraint programming (ccp) is a model of concurrencyfor systems in which agents (also called processes) interact with one another bytelling and asking information in a shared medium. Timed (or temporal) ccp ex-tends ccp by allowing agents to be constrained by time requirements. The noveltyof timed ccp is that it combines in one framework an operational and algebraicview based upon process calculi with a declarative view based upon temporallogic. This allows the model to benefit from two well established theories used inthe study of concurrency.This essay offers an overview of timed ccp covering its basic background andcentral developments. The essay also includes an introduction to a temporal ccpformalism called thentcc calculus.1 IntroductionConcurrency theory has made progress by extending well-established models of com putation to capture new and wider phenomena. These extensions should not come as asurprise since the field is indeed large and subject to the advents of new technology. Oneparticular phenomenon, for which extensions of the very first theories of concurrencywere needed, is the notion of time.Time is not only a fundamental concept in concurrency but also in science at large.Just like modal extensions of logic for temporal progression study ...