Fair processes

Abstract

We study the notion of fairness in Petri Nets using processes, which are partially ordered sets, to describe their semantics. Processes do not contain more causality than the one specified in the marked net. We define, in a hierarchical way, transition-fair processes and marking-fair processes. Conspiracy phenomena may be encompassed by this hierarchical definition. We show that a process is transition-fair iff any of its associated occurrence sequence is transition-fair. We show that the hierarchy does not collapse in general for transition-fairness and that it does collapse for marking-fairness. Finally, implications between transition-fairness and marking-fairness are studied for three classes of marked nets.