M.P. Koutny
A. Yakovlev
University of Newcastle upon Tyne. 1995.
This paper extends the theory of regions developed by Nielsen, Rozenberg and Thiagarajan within a set-theoretic framework, to accommodate the class of non-pure nets and their transition systems. Those are called semi-elementary nets and semi-elementary transition systems, respectively. The main motivation of such an extension is practical, the need to model asynchronous hardware structures, where certain events happen only when some conditions (these are called co-conditions) are true but without changing the state of these conditions. One of the applications of this theory is synthesis of Petri net models from state-based specifications. As an example we present a Petri net model of control of a counterflow pipeline for Sproull's asynchronous processor. This control was originally specified as a transition system which did not satisfy elementarity axioms of Nielsen et al.