Modelling Groups for Group Communications

This paper presents a general model of a Group Management Service (GMS) which is designed to support collaborative interactions among groups of distributed users using di erent applications. There are two main bene ts of such a service. Firstly, it would be easier to implement new collaborative applications because of the possibility to use an existing service. Secondly, it would be possible for di erent applications to share collaboration relevant information because of a common database of information about users and groups maintained by the GMS. One important property of the GMS is its exibility with respect to the information stored. It is possible to store application-independent as well as application-dependent information. Using an object-oriented approach, applications can share the application-independent information (such as a group's members and administrative information) and can also use the GMS to store application-dependent information which can only be interpreted by a closed set of applications (those who know the syntax and semantics of the application-dependent information). The model of the GMS is very simple and consists mainly of two classes of objects, namely user and group. A small set of operations is provided for querying and modifying GMS information. The possibility to store application-dependent information is realized by allowing using application to create derived classes (ie subclasses) of the classes user and group. Thus it is possible for applications using the GMS to implement their own user and group classes without losing the ability to manage these objects with the GMS. Two applications are presented which may use the GMS to manage their users and groups. Both applications use applicationspeci c derived classes of user and group. However, it is still possible for these applications to share the application-independent information of their users and groups.