Message sequence charts in the software engineering process

The software development process benefits from the use of Message Sequence Charts (MSC), which is a graphical language for displyaing the interaction behaviour of a system. We describe canonical applications of MSC independent of any software development methodology. We illustrate the use of MSC with a case study: the Meeting Scheduler

On the testability of SDL specifications

The problem of testing from an SDL specification is often complicated by the presence of infeasible paths. This paper introduces an approach for transforming a class of SDL specification in order to eliminate or reduce the infeasible path problem. This approach is divided into two phases in order to aid generality. First the SDL specification is rewritten to create a normal form extended finite state machine (NF-EFSM). This NF-EFSM is then expanded in order to produce a state machine in which the test criterion may be satisfied using paths that are known to be feasible. The expansion process is guaranteed to terminate. Where the expansion process may lead to an excessively large state machine, this process may be terminated early and feasible paths added. The approach is illustrated through being applied to the Initiator process of the Inres protocol

Expanding an extended finite state machine to aid testability

The problem of testing from an extended finite state machine (EFSM) is complicated by the presence of infeasible paths. This paper considers the problem of expanding an EFSM in order to bypass the infeasible path problem. The approach is developed for the specification language SDL but, in order to aid generality, the rewriting process is broken down into two phases: producing a normal form EFSM (NF-EFSM) from an SDL specification and then expanding this NF-EFSM

The Oracle Problem When Testing from MSCs

Message Sequence Charts (MSCs) form a popular language in which scenario-based specifications and models can be written. There has been significant interest in automating aspects of testing from MSCs. This paper concerns the Oracle Problem, in which we have an observation made in testing and wish to know whether this is consistent with the specification. We assume that there is an MSC specification and consider the case where we have entirely independent local testers (local observability) and where the observations of the local testers are logged and brought together (tester observability). It transpires that under local observability the Oracle Problem can be solved in low-order polynomial time if we use sequencing, loops and choices but becomes NP-complete if we also allow parallel components; if we place a bound on the number of parallel components then it again can be solved in polynomial time. For tester observability, the problem is NP-complete when we have either loops or choices. However, it can be solved in low-order polynomial time if we have only one loop, no choices, and no parallel components. If we allow parallel components then the Oracle Problem is NP-complete for tester observability even if we restrict to the case where there are at most two processes

Operational semantics for MSC'96

Recently, the ITU-standardised specification language Message Sequence Chart has been extended with constructs for more complete and structured specifications. The new version of the language is called MSC'96. Currently, research is performed on the extension of the formal semantics towards a semantics for MSC'96. In this article, we aim at explaining the basic ideas behind the formal semantics. We give formal definitions of parts of the language, but most features are explained by informal examples and drawings. It takes several steps in order to follow the path from an MSC drawing to its formal meaning. First, the drawing must be converted to a concrete textual representation. This conversion is already defined implicitly in Z.120. Next, this syntax is transformed into a formal expression over some process algebra signature. MSC constructs are replaced by appropriate process algebra operators. This transformation is compositional. The operational behaviour of the process algebraic expression can be studied, or the expression can be interpreted into some mathematical model and compared to the interpretation of some other MSC

Test des protocoles et services liés à la mobilité

Les fortes avancées technologiques dans le domaine des réseaux entraînent la conception de nouveaux protocoles et la création de nouveaux services. Ces nouveaux protocoles et services mettent en relation des éléments hétérogènes qu’il convient de tester pour garantir leur conformité et leur interopérabilité. Pour ce faire, nous avons adopté les normes WAP et UMTS et proposé une méthodologie de test de la couche applicative WAE (à travers une application écrite en WML), des couches protocolaires WSP et WTP du WAP et des services de localisation dans le réseau UMTS. Ces tests ont été par la suite mis en oeuvre dans une plate-forme afin de vérifier que les échanges protocolaires sont conformes aux spécifications et que les différentes entités peuvent interagir correctement.The strong advances in the field of networks involves the design of new protocols and the creation of new services. These new protocols and services connect heterogeneous elements which must be tested to guarantee their conformity and their interoperability. With this intention, we adopted the WAP and UMTS standards, and proposed a methodology to test the WAE applicative layer (through an application written in WML), WAP WSP and WAP WTP layers, and UMTS location services. Thereafter these tests have been implemented in a real platform in order to check that the exchanges are in conformity with the specifications and that the various entities can interact correctly

Automatic synthesis of SDL from MSC and its applications in forward and reverse engineering

Abstract Wider adoption of formal specification languages in industry is impeded by the lack of support for early development phases and for integration with older, legacy software. Methodology aimed at improving this situation is presented. The methodology uses Message Sequence Charts (MSC) as a "front-end" specification language and systematically applies an automatic synthesis technique to produce executable specifications in the telecommunications standard Specification and Description Language (SDL). Applications of the automatic synthesis technique for both forward and reverse engineering are demonstrated