Many object-oriented toolkits and frameworks for groupware development provide shared objects as a basic service. This relieves developers of a lot of problems originating from the field of distributed systems. However, there is little support on how to use shared objects to actually build collaborative applications. In this paper we propose an object-oriented model for applications using shared objects. The model is discussed with respect to object-oriented reusability aspects and its applicability is tested against CSCW-specific aspects like the provision of group-awareness and coupling control. Furthermore, concrete model examples derived from an example application are shown for illustration.

This paper introduces COAST, an object-oriented toolkit for the development of synchronous groupware, which enhances the usability and simplifies the development of such applications.COAST offers basic and generic components for the design of synchronous groupware and is complemented by a methodology for groupware development.Basic features of the toolkit include transaction-controlled access to replicated shared objects, transparent replication management, and a filly optimistic concurrency control.Development support is provided by a session concept supporting the flexible coupling of shared objects' aspects between concurrent users and by a fully transparent updating concept for displays which is based on declarative programming.