What synchronous groupware needs: notification services

Synchronous groupware is the class of applications in which two or more people collaborate in what they perceive to be real time. Most previous efforts to deploy synchronous groupware have failed. The author argues that: synchronous groupware can often be deployed independently of system support for audio, video, or persistent storage; deployment and maintenance of different synchronous groupware applications becomes more reasonable if those applications can share and reuse a common coordination infrastructure, called a notification service; and the most likely way to achieve such sharing and reuse is by the definition of a common notification service protocol. At Lotus, we have designed and implemented such a protocol, called the Notification Service Transfer Protocol (NSTP). Our implementation, called PlaceHolder, has been available from our Web site since November 1996.