Virtual time and virtual space

Simulation models involve the concepts oftime andspace. In designing a distribution simulation programming system, introducing a temporal construct results in a specification language for describing a changing world, introducing a spatial construct makes it possible to coordinate multiple, simultaneous, nondeterministic activities.In this paper, we present a new distributed logic programming model and discuss its implementation. A distributed program is represented by avirtual space—a set of process which are logical representations of system objects, and is evaluated with respect tovirtual time—a temporal coordinate which is used to measure computational progress and specify synchronization. The major focus of the implemention is the ability to accomplish global backtracking. The proposed implementation collects global knowledge through interprocess communication, controls global backtracking distributedly according tovirtual time anddependency relations, and capture heuristics in that earlier synchronizations may make subsequent synchronizations more likely to succeed.As compared with other distributed logic programming systems, our system provides a simpler syntax, well-defined semantics, and an efficient implementation.