Programming in Timed Concurrent Constraint Languages

Vijay A. Saraswat, Radha Jagadeesan, Vineet Gupta

Introduction

This paper explores the expressive power of the tcc paradigm. The origin of the work in the integration of synchronous and constraint programming is described. The basic conceptual and mathematical framework --- developed in the spirit of the model-based approach characteristic of theoretical computer science --- is reviewed. We show that a range of constructs for expressing timeouts, preemption and other complicated patterns of temporal activity are expressible in the basic model and language-framework. Indeed, we present a single construct on processes, definable in the language, that can simulate the effect of other preemption constructs.

We present Timed Gentzen, a concrete tcc language instantiated over the ``generic'' constraint system Gentzen that underlies ``unification-free'' computation in (classical, intuitionistic, linear) logic. Subsequently, we present solutions to several representative reactive and synchronous programming problems in Timed Gentzen; also we discuss how some common default inferencing techniques can be represented. We discuss and include a full working interpreter for Timed Gentzen, written in prolog, that can be used for running these programs. It is short, under a hundred lines long, but fully functional.

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