A Network of Communicating Logic Programs and Its Semantics

Abstract

In this paper, a network of ccmnunicating logi c programs is proposed as a rrodel for parallel/ concurrent progranming .based on logic programs. This network is regarded as an extension of Kahn's prre dataflow in the sense that nodes are logic programs which have atans for receiving am. serrling messages as well as queues to accept am. memorize them. The nodes' behaviour is unboundedly noooeterministic. On the assumption that the channels' denotations should be defined by using sequence danains, the main concern of the present paper is whether or not mathematical semantics is always well-defined for a given network even when it is of unbounded norX!eterminism. This paper will show that the proposed network is reduced to a dataflow when a kioo of 'fairness' is asked for nondeterminism in which logic programs receive inputs am. produce outputs based on their c::cmpltations. The network, then, has a (least) fixpoint semantics; it is regarded as one of mathematical semantics of the network, since it can satisfy the recursive relations among the channels' denotations . It is also stated that the network with fair merge operators is applicable to the realization of a canputational mechanism for sequential ligic programs.