Transparent and flexible data sharing for synchronous groupware

Synchronous groupware brings together users, who are geographically distributed and connected via a network. It encompasses a wide range of applications like collaborative whiteboards, text editors or virtual environments. Developing synchronous groupware is a difficult and time-consuming task, an application has to establish network connections between the collaborating users, handle parallel input from many users, has to offer group functions for collaboration-awareness, and has to manage shared data. The latter belongs to the main obstacles during the development of synchronous groupware. This thesis describes DreamObjects. DreamObjects is a platform that focuses on shared data management. It offers flexible and extensible solutions for the recurring problems that are related to data sharing and achieves a maximum of transparency for the developer, as it hides all necessary mechanisms for managing the shared state. DreamObjects supports a variety of distribution schemes. The data of an applica-tion can be distributed to one developer-selected site, all participating sites, or a dynamically changing set of the participating sites. Similarly, a developer can choose between different mechanisms for concurrency control. If the offered solutions do not meet the requirements of the application, developers can even integrate their own solutions in the platform. A user, who joins a session, can choose, whether he wants to join with a replay of the session or with a direct state transfer. Both mechanisms are fault-tolerant, decentralized, and do not block current participants of the session in their work. Finally, DreamObjects offers a decentralized persistency service to support the transition between asynchronous and synchronous work.