This study integrates computer-supported co-operative work (CSCW), workflow management systems (WFMS), and transaction processing (TP) technologies by first presenting a rigorous analysis of requirements presented by diverse classes of co-operative applications, ranging from co-operative authoring, through design for manufacturing, to interorganizational workflows. It then introduces a language that is suitable for the specification of co-operative activities. This language is based on a formal model and provides a collection of tools which allow the users to reason about the correctness of specifications, rather than relying on mechanisms that detect possible violations at run-time. The transaction model introduced in this monograph combines the use of private work spaces that allow individual participants to work independently, with synchronization mechanisms that allow them to combine their work to form a coherent whole. Finally, this monograph shows how the new transactional concepts developed in the project can be mapped into the transaction manager of an object-oriented database management system to provide a clean and efficient implementation. The book summarizes the state of the art of key technologies in co-operative activities and transactions. It should be useful to students, researchers, and technology developers in the areas of computer-supported co-operative work (CSCW), workflow management systems (WFMS), and transaction processing (TP) technologies, and is suitable as a text or reference for a graduate-level course on database systems or computer supported co-operative work.