A MODEL FOR DISTRIBUTED SYSTEMS BASED ON GRAPH REWRITING

In our model, a graph describes a net of processes communicating through ports and, at the same time, its computation history consisting of a partial ordering of events. Stand-alone evolution of processes is specified by context-free productions. From productions and a basic synchronization mechanism, a set of context-sensitive rewriting rules that models the evolution of processes connected to the same ports can be derived. A computation is a sequence of graphs obtained by successive rewritings. The result of a finite computation is its last graph, whereas the result of an infinite computation is the limit, infinite graph defined through a completion technique based on metric spaces. A result characterizes a concurrent computation, since it abstracts from any particular interleaving of concurrent events, while in the meantime providing information about termination, partial or complete deadlocks, and fairness.