ISSUES AND EXPERIENCES DESIGNING AND IMPLEMENTING TWO GROUP DRAWING TOOLS

Abstract

Groupware designers are now developing multi-user equivalents of popular paint and draw applications. Their job is not an easy one. First, human factors issues peculiar to group interaction appear that, if ignored, seriously limit the usability of the group tool. Second, implementation is fraught with considerable hurdles. In particular, contemporary window systems and their user interface toolkits actually inhibit implementation efforts by failing to provide adequate building blocks for constructing group interface primitives and by not supplying an adequate architectural infrastructure. This paper describes the issues and experiences we have met and handled in the design of two systems supporting remote real time group interaction: \fIGroupSketch\fR, a multi-user sketchpad; and \fIGroupDraw\fR, an object-based multi-user draw package. On the human factors side, we summarize empirically- derived design principles that we believe are critical to building useful and usable collaborative drawing tools. On the implementation side, we describe our experiences with replicated versus centralized architectures, schemes for participant registration, multiple cursors, network requirements, and the structure of the drawing primitives.