A Petri Net Definition of a System Description Language

This paper introduces a language, Epsilon, for the description of systems with concurrency, and presents a formal definition of Epsilon's semantics. The language is based on Delta ‹ the first major attempt to create a language solely aimed at system description without the restrictions placed on languages executable on digital computers. The design of Delta was itself heavily influenced by the experience from the development and use of Simula.It is not obvious what kind of semantics a system description language should have. The situation is more complex than with normal algorithmic languages and none of the existing semantic approaches appear to be satisfactory.To clarify the situation, we first describe the language Epsilon, which contains only a few basic primitives. Then we define the semantics of Epsilon by means of a formal model based on Petri nets. The model called ''Concurrent systems'' is an extension of Petri nets with a data part and with expressions attached to transitions and to places. The model is a further development of formalisms proposed by R.M. Keller and A. Mazurkiewicz. The expressions attached to places is a novel feature and is used to define continuous transformations on the data part. The semantics of a given system description is defined in terms of firing sequences of the corresponding concurrent system.To be presented at the Evian Conference on Semantics of Concurrent Computations, July 1979