Token dispensers for GSS race conditions: locking things that don´t exist

A technological challenge that distinguishes group support systems (GSS) from many other technologies is the need to accommodate a variety of race conditions. A race condition occurs when two or more users of the same shared data object execute processes on that object that could produce conflicting results. Some particularly challenging race conditions obtain when users contend for the right to create resources that do not yet exist. Resources that do not yet exist are not available to be locked. This paper offers token dispenser technology as a general-purpose solution for addressing a variety of race conditions, including those where end user clients contend for resources that do not yet exist. The paper describes the details of an implementation of token dispensers as a plug-in service under the Apollo architecture (an open architecture for collaborative clients and servers). The paper summarizes the results of field trials of the token dispenser implementation by developers and end users. It concludes with discussion of future directions for token dispenser research.