Jan Schümmer, Till Schümmer and Christian Schuckmann work at GMD-IPSI, where they develop groupware applications such as collaborative learning systems (VITAL, L³), software for collaborative buildings (BEACH), or collaborative software development tools (TUKAN or cooperative UML-Editor). All these Systems are based on COAST, which was developed by the speakers after they built the meeting support system DOLPHIN. More information about these systems and the COAST framework can be found at the IPSI homepage ( or at the COAST homepage (

Groupware applications help a group of distributed or co-located users to work on a common task. Synchronous groupware applications enable a group of users to collaborate in real-time. Building synchronous groupware applications is much more complicated than building single user applications. Thus we developed the COAST framework, which reduces the load of development of groupware applications to a level of single user application. The COAST framework therefore offers a data description language to model the (shared) domain model, provides mechanisms for synchronous manipulation of the shared domain model by a set of users, keeps the shared model and their visualizations at a consistent state, supports the provision of clues about other user’s activities (group awareness), includes a pre-defined extensible model of users and their work environments, and assists the developer in modeling user interaction and collaborative sessions. COAST is implemented in VisualWorks Smalltalk and is becoming open source, to be used by a large community for the development of groupware. The talk will give an introduction to COAST’s concepts for groupware development and discuss the design decisions we made during it’s development.