A technique for applying formal message sequence specifications to the full definition of systems is presented. The technique supports automatic transformation of message sequence descriptions into communicating process descriptions that implement the sequences. It also supports hierarchical verification of protocols in the message sequences and process descriptions. Both a language for message sequence description, SAL, and a design support environment, SDE, have been developed based on the proposed technique. To collectively and hierarchically describe message sequences, SAL can compose message sequences from message sequence elements. By adding SAL descriptions, SDE supports the incremental specification and development of communications software: consistency between the added sequences and existing software is verified, and the existing software is automatically updated. This support especially contributes to the efficient maintenance of communications software. The feasibility and usefulness of the proposed technique are demonstrated by experimental application of SDE to PBX.>

This paper describes specification and verification technology for software development. This technology consists of 1) a Specification description language called LAN-S, 2) a compiler to generate data for specification verification, and 3) a specification analysis algorithm (analyzer). A switching system and terminals are regarded as state transition machines in this technology. From specifications described in LAN-S, input data for the specification analyzer are generated. The analyzer incorporates a concept of the reduced reachability tree (RRtree), which can solve the "state space explosion" encountered in the ordinary teachability tree analysis. Using some subprocedure libraries, the switching software specification in LAN-S is transformed into an executable control program for a system with "process based software architecture." When applied to software development for a model switching system SPICE, the analyzer produced a reachability tree smaller than the one produced via the ordinary reachability tree analysis by 99.95 percent, and proved to be applicable to practical systems analysis.

This paper proposes a simple procedure for the design of small-diameter graphs. It can be used to construct a directed graph whose diameter is less than or equal to that of any previously proposed graph.

This paper proposes a simple algorithm for the graph design of small-diameter networks. For given nodes n and degree d, this algorithm can be used to construct a directed graph with diameter ⌈logd n⌉, which is at most one larger than the lower bound ⌈logd (n(d − 1) + 1)⌉ − 1. Its average distance is also close to the lower bound. The algorithm can be used to construct a directed graph with smaller diameter, compared with any other conventional methods, when n is larger.