Reduced reachability graphs with parallel actions and dynamic replacement

Analysis of communication protocols by the conventional state exploration is a well known technique. It is actually implemented in several tools of validation. The major problem of this technique is its restricted applicability and depends on the available memory. The number of reachable states is often large and sometimes infinite. In this paper we discuss a reduction technique to build small graphs as possible which preserve same properties. At this end vectors of executable actions are proposed to eliminate redundancy of sequences and intermediate states. The depth-first and the breadth-first algorithms based on the concept of dynamic replacement are used in the order to reduce the final graphs. Two major questions are discussed: the finiteness of the graphs and the verification of the communication properties