An Object-Oriented Approach To Dynamic Service Descriptions

The former CCITT has defined a methodology, consisting of three stages, to evolve from a set of service descriptions to a protocol definition that supports these services. In the first stage, the service is described from a user's viewpoint. A part of this first stage consists of the descriptions of the dynamic behaviour of the service. The introduction of this paper elaborates on the interpretation of the 'user's viewpoint' of dynamic service descriptions. In the subsequent sections we introduce an object-oriented approach to define a framework for the dynamic service descriptions. The flexible definition of services is facilitated by decomposing the service into a standard set of building blocks, referred to as service objects. A service object is the smallest service element that a user can independently reference and manipulate. By modelling in terms of service objects, we avoid the presumption that the total service consists of a specific number of parties or connections. The definition of a service mainly consists of imposing additional semantic rules on the way service objects can be manipulated within the context of that service. The complete system will thus consist of a service-specific part and a generic part, i.e. a part which is common to all services. An overview of the system configuration and the behaviour of the generic part is illustrated by SDL Descriptions.1 Finally, we illustrate the method by describing a typical multiconnection multiparty service. The work presented within this paper is based on the results of the RACE MAGIC project.2