Token transition graphs: a new way to express multitasking requirements

In prior developments of discrete event simulation of distributed architectures, difficulty has been encountered in capturing good concurrency abstractions. The above problem is addressed in the paper. Because of the nature and complexity of certain concurrency concepts, a new mode of representation was deemed necessary to express their details compactly and understandably. Consequently, an extension to statecharts was devised wherein tokens (representing objects) circulate through the graphs. One or more tokens may migrate between nodes as a single event in accord with transition predicates that acknowledge token locations and their respective states or attributes. A substantial increase in practical expressive power is therefore enabled through the use of multiple tokens and multilevel status information. This type of representation has been termed a token transition graph. For illustrative purposes, a token transition graph is applied in representing the dynamics of a very basic rate monotonic scheduling algorithm, where the tokens denote tasks to be scheduled