A framework for flexible coupling in groupware widgets

Modern Computer-Supported Cooperative Work (CSCW) applications are driven by intensive graphical user interfaces. Groupware widgets, such as shared scrollbars and text editors, are common in these applications to facilitate synchronisation of shared information across a group of users. These widgets differ from their single-user counterparts in the way that actions performed on them must be readily reflected on the displays across a user group. Many of these groupware widgets are converted from their single-user counterparts by adding facilities for coupling the widget properties. The conversion involves determination on the properties by which groupware widgets should be synchronised, under what circumstances and to what extent they are synchronised. These properties define the coupling of groupware widgets. Flexibility in coupling, therefore, refers to the degrees of coupling that the CSCW system allows. A promising approach to supporting flexible coupling in CSCW systems is the use of notification service. In this approach, the shared data model is kept in a notification server and replicated by a number of replicas located at the client sides. Each replica receives state-change notification messages from the notification server and determines a specific presentation of the data. This approach requires notification event handling at the client sides. However, handling notification events at the client sides makes it difficult to have a central management over the coupling behaviours of a CSCW system. This central management is useful when the changes of the collaboration patterns are required to take place synchronously. In addition, the diversity of the collaboration behaviours, which are often affected by different characteristics of group behaviours, necessitates the ability of clients to respond to pattern changes. Therefore, it is beneficial to abstract the coupling pattern of the system and put this piece of information in a central repository. By means of this repository, dynamic changes in collaboration patterns can be achieved by modifying the installed coupling information in the course of collaboration. To support central management of coupling patterns and maintain a high degree of flexibility, a new framework for notification service that allows coupling behaviours to be dynamically controlled in a centralised server is proposed. In addition, this framework allows the coupling pattern to be utilised and modified over time, which enables the system to adapt to various collaboration needs and group tailoring. This thesis will highlight the details of the implementation of the proposed framework. A groupware web browser has also been developed on top of it to demonstrate how flexible coupling can be implemented and managed in practice. This thesis also evaluates the performance and discusses on the scalability issue