Using Roles With Types And Objects For Service Development

This paper is about achieving open ended-ness and flexibility using roles, types and objects. Roles are increasingly popular modeling notions. Unfortunately the term "role" is used to mean different things in different approaches, and it is not always clear how it relate to other important notions such as types or classes and objects. The paper seeks to clarify what roles are and how they can be utilized to achieve open-ended flexibility in systems and services. It will not go deeply into the technical details, but concentrate on overall principles and how they may be utilized in combination with existing methods and languages, in particular UML [OMG 99], SDL [ITU 93] and MSC [ITU 96b]. It is not reasonable to believe that service logic in the future will fit into a monolithic pre-defined framework, like the IN architecture. It is more likely that service logic will be provided by open-ended "object communities" that are allowed to evolve and change more freely as long as the result is useful and without undesirable effects. One idea that will be presented here is to associate required and provided behaviour roles with types, so that provided and required roles may be aligned when objects of the types are linked together. Not only does this enable an incremental validation of links to take place, it also opens the possibility that objects may learn to play roles dynamically and thereby dynamically adapt to new services and situations. =5?!@8A0BC?5D;EFGA:HI5EJFLKJM5NO?5=QPRESA:FLT;MOU5EM5EJBCKD According to normal terminology, objects are phenomena; i.e. tangible entities with substance and behaviour, while types are concepts representing the features shared by all objects belonging to the type and roles are properties that may be associated with both objects an..