Workflows have been widely used for coordinating structured processes, whereas group support systems are used to facilitate ad hoc and unstructured collaboration activities. In many business settings, it is beneficial to use both workflows and group support systems. However, how to integrate workflow systems and group support systems have not been well studied in the literature. In this paper, we propose a scalable middleware framework, namely event management system, which can support high-degree decoupling between workflow and groupware. The event management architecture and its main functionalities as well as the implementation techniques are presented. We delineate the applicability of event-based integration by comparing with other integration paradigms.