摘要：Event structures are a well-accepted model of concurrency. In a seminal paperby Nielsen, Plotkin and Winskel, they are used to establish a bridge betweenthe theory of domains and the approach to concurrency proposed by Petri. Abasic role is played by an unfolding construction that maps (safe) Petri netsinto a subclass of event structures, called prime event structures, where eachevent has a uniquely determined set of causes. Prime event structures, in turn,can be identified with their domain of configurations. At a categorical level,this is nicely formalised by Winskel as a chain of coreflections. Contrary to prime event structures, general event structures allow for thepresence of disjunctive causes, i.e., events can be enabled by distinct minimalsets of events. In this paper, we extend the connection between Petri nets andevent structures in order to include disjunctive causes. In particular, we showthat, at the level of nets, disjunctive causes are well accounted for bypersistent places. These are places where tokens, once generated, can be usedseveral times without being consumed and where multiple tokens are interpretedcollectively, i.e., their histories are inessential. Generalising the work onordinary nets, Petri nets with persistence are related to a new subclass ofgeneral event structures, called locally connected, by means of a chain ofcoreflections relying on an unfolding construction.
关键词：Computer Science - Logic in Computer Science;F.1.2;F.3.2;F.4.1
