Supporting Cooperative Work by Conventional Database Transactions

‘Computer-Supported Cooperative Work’ (CSCW) is a young, interdisciplinary research area considering applications with strong demands on multiple fields of computer technology, e.g., distributed systems and networks or multi-media systems. In this paper, we will be focusing on the information-sharing and the corresponding activity-control aspect. Here, the conventional transaction concept of database systems lacks adequate cooperation control capabilities. A database transaction is not the appropriate operational unit for the sequence of actions/operations performed by a cooperating user because the isolation property builds protective walls to concurrently active users. Given this background many new approaches to transaction modelling are making these protective walls more permeable. While most advanced transaction models continue to apply a transparent concurrency control, in groupware systems a user-centered approach to cooperation control is needed reflecting the highly dynamic work and the rich patterns of interpersonal cooperation. Therefore, we propose an explicit cooperation control. Although, database transactions do not have cooperative capabilities, we claim that they are still applicable, even in groupware applications. The work of a cooperating user contains several elementary actions. Due to preserving basic consistency, a transaction-protected execution of these elementary actions is needed. Thus, we propose to enhance the traditional transaction processing concept by an additional layer supporting explicit cooperation control. In this paper we will discuss the interplay of implicit concurrency control and explicit cooperation control using our CONCORD model (CONtrolling COopeRation in Design Environments) as a sample approach to activity modeling in groupware systems.