SDE - INCREMENTAL SPECIFICATION AND DEVELOPMENT OF COMMUNICATIONS SOFTWARE

Message sequences are peer protocol descriptions representing the partial behaviors of systems and they are suitable for service description. Message sequences, however, are used only to provide a preliminary to the full definition of systems. This paper proposes a technique for applying formal message sequence specifications to this full definition. The technique supports automatic transformation of message sequence descriptions into communicating process descriptions that implement the sequences. It also supports hierarchial 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 is demonstrated by experimental application of SDE to PBX.