In: Proc. of the 1988 IEEE Workshop on Visual Languages Pittsburgh,, pages 168-174. Washington: IEEE Computer Society Press, 1988.
Abstract: The PFG language is a parallel programming language with graphical syntax. Its formal operational semantics are expressed by the hierarchical graph model of concurrent real-time software systems. Informally, each procedure in a PFG program is a hierarchical graph expressing the data state and a place-timed Petri net expressing the possible parallel threads of control operating the data state.