CPSC 689/602--Spring 1997
Computer-Supported Cooperative Work

Paper Report

Title: Replicated Architectures for Shared Window Systems: A Critique
Authors: J. Chris Lauwers, Thomas A. Joseph, Keith A. Lantz and Allyn L. Romanow
Citation: 1990 ACM 089791-358-2/90/0004/0249
Reprinted in: Baecker R. M., Readings in Groupware and Computer-Supported Cooperative Work 1993, pp. 651-662.

This paper is a critique on replicated architectures for shared window systems. Shared window systems allow participants to share existing single-user (collaboration-transparent) applications. A shared window system consists of a conference agent that interposed between applications and the window system.

The authors presented their motivations for adopting replicated architectures for shared window systems. Their motivations include performance, lower network bandwidth, versatility, and heterogeneity. However, replicated architectures do have some drawbacks. Some of these issues include synchronization, consistency, and single-execution semantics.

Various sources of possible input inconsistency are addressed. Input inconsistency sources could be from user input, environments variables, file, window managers, and inter-process communication. Another major concern is the ordering of input from multiple sources. The authors also gave two examples where non-deterministic input can be tolerated: polling the input queue, and discarding input events.

Finally, designers of replicated architectures for shared window systems has to deal with output consistency and start-up consistency. Sometimes, minimum modifications to existing applications are required. By introducing collaboration-awareness into existing applications and/or servers, designers can eliminate most of the problems associated with application replication.

Report prepared by: Yew Kuan Choo, Email: ykchoo@cs.tamu.edu
Discussion date: 3-21-97 Report date: 3-23-97