Communications service synthesis from informal specifications and sequence diagrams.

Abstract

Communications Networks consist of layers where each layer provides a service to the layer above. A service consists of phases each of which is a sequence of message interactions intended to achieve a specific user goal [Boyc 90]. For example, Transport Service has three phases: connection establishment, data transfer and connection release. Recent research [Dsou 95] and [Sale 96] has emphasized the need for systematic methods to build services. We propose such a method to build a Global Service FSM (Finite State Machine) from a set of Sequence Diagrams. We use these diagrams to capture a set of constraints on the service: local, end-to-end and concurrency constraints. The service synthesis method is composed of a series of algorithmic steps. The two major steps are: (i) construction of Phase Scenario Machines (PSM), (ii) coupling of PSMs at the phase boundaries. The resulting FSM, called a Global Scenario Machine (GSM), is a more precise and complete model of the global service. This thesis shows that a global service specification, the Global Scenario Machine can be semiautomatically and systematically built from a set of sequence diagrams. More work is needed on tools and verification methods to insure the completeness of this approach and its ease of use, but a realistic case study is used illustrate the feasibility of the approach.