A taxonomy of architectures for synchronous groupware applications

Abstract

I offer a taxonomy for characterizing various architectures for synchronous groupware applications. Unlike teleconferencing per se, these are applications that have been implemented in such a way that users may simultaneously interact with the applications. The analysis rests on the following two premises:• The primary challenge tot synchronous groupware applications is to ensure state consistency,and• Applications may be divided into four levels of state.Figure 1 below depicts the four levels of state that I envision within any application. 4 The display state is the information that drives the user's display; the view state is the information that relates the user's display to the underlying information in the application; the model is the underlying information; and, the file is a persistent representation of the underlying information.Figure 1 5 below depicts the situation for a single user application. With multiple users there will be multiple displays, one per user. In synchronous groupware, one must ensure that these displays have access to some form of consistent state. There are two ways to achieve this consistency: by maintaining only one copy of the state or by maintaining multiple copies and using a consistency maintaining protocol. The next three sections discuss various architectures derived by applying these two approaches to consistency. The last section discusses a variety of residual issues that the evolving taxonomy does not easily address.