An operator net model for distributed systems

An operator net is a graph consisting of nodes and directed arcs. While operator nets are syntactically similar to dataflow nets, they completely separate the operational semantics from the mathematical semantics. In this paper we define an operational semantics for operator nets that intuitively corresponds to communication in a distributed system. The operational semantics of operator ator nets provide a formal model for a distributed system that is an intermediate point between the actual system and a mathematical model. Abstract properties are expressed using relations on events and messages of an operator net. Corresponding operational specifications can be written using Lucid equations that define a node as a mathematical function on infinite history sequences. The operational specifications are executable and can be easily transformed into a practical implementation of the system. Examples of such specifications are included in the paper.Janice Glasgow is an associate professor in the Department of Computing and Information Science at Queen's University. She received her M. Math and Ph.D. degrees from the University of Waterloo. Dr. Glasgow's current research interests include programming language semantics and logics for reasoning about programming.Glenn H. MacEwen r received the B.Eng. degree in electrical engineering from McGill University, Montreal, P.Q., Canada, in 1962 and the M.Sc. and Ph.D. degrees in computer science from the University of Toronto, Toronto, Ont., Canada in 1967 and 1971, respectively. Since 1970 he has been with the Department of Computing and Information Science at Queen's University, Kingston, Ontario. He served as Head from 1982 to 1987 and is currently a Professor in the department. He is also a director and consultant to Andyne Computing Limited. His research interests include software engineering, computer security, and real-time systems. Dr. MacEwen is a senior member of the Institute of Electrical and Electronics Engineers, and a member of the Association for Computing Machinery and the Association of Professional Engineers of Ontario.