Integrated Temporal Reasoning with Periodic Events

Abstract

In many areas of Computer Science, including planning, workflows, guidelines, and protocol management, one has to deal with abstract plans, procedures, or schedules involving temporal constraints between classes of actions that have to be repeated at periodic times and may be instantiated in different ways for different executions of the plans (procedures, schedules). In this paper we propose an integrated framework to deal with both qualitative temporal constraints on classes of actions and temporal constraints between instances of actions, in which temporal reasoning is used to amalgamate both types of constraints and to check their consistency. In particular, we consider an expressive formalism to deal with temporal constraints between classes of actions (with special attention to periodic actions) which takes into account different components such as frame times, numeric quantification, periods, and qualitative relations. We define the notions of (contextual) concretization of qualitative temporal constraints between classes and use this notion to formally define the consistency of a knowledge base of temporal constraints between classes and a set of temporal constraints on instances, and to define the algorithm for checking such a consistency. An application for scheduling lessons in a school is shown in an example.