Products of message sequence charts

Abstract

An effective way to assemble partial views of a distributed system is to compute their product. Given two Message Sequence Graphs, we address the problem of computing a Message Sequence Graph that generates the product of their languages, when possible. Since all MSCs generated by a Message Sequence Graph G may be run within fixed bounds on the message channels (that is, G is existentially bounded), a subproblem is to decide whether the considered product is existentially bounded. We show that this question is undecidable, but turns co-NP-complete in the restricted case where all synchronizations belong to the same process. This is the first positive result on the decision of existential boundedness. We propose sufficient conditions under which a Message Sequence Graph representing the product can be constructed. © 2008 Springer-Verlag Berlin Heidelberg.