Communication theories and technology have tended to focus on extended, formal meetings and have neglected a prevalent and vital form of workplace communication—namely, lightweight communication. Unlike formal, extended meetings, lightweight interaction is brief, informal, unplanned, and intermittent. We analyze naturalistic data from a study of work-place communication and derive five design criteria for lightweight interaction systems. These criteria require that systems for lightweight interaction support conversational tracking, rapid connection , the ability to leave a message, context management, and shared real-time objects . Using these criteria, we evaluate existing interpersonal communications technologies. We then describe an implementation of a system (TeleNotes) that is designed to support lightweight interaction by meeting these criteria. The interface metaphor allows communications to be based around desktop objects, resembling “sticky notes.” These objects are also organized into “desktop piles” to support conversational threads and provide mechanisms for initiating real-time audio, video, and application sharing. We conducted informal user testing of several system prototypes. Based on our findings, outstanding issues concerning theory and systems design for communication systems are outlined—in particular, with regard to the issue of managing conversations over time.

We introduce the Notification Service Transfer Protocol (NSTP), which provides a simple, common service for sharing state in synchronous multi-user applications. A Notification Server provides items of shared state to a collection of clients and notifies the clients whenever one of the items changes. The division between client and server in this system is unusual; the centralized state is uninterpreted by the server. Instead, the responsibility for semantics and processing falls on the clients, which collude to implement the application. After describing NSTP, we differentiate it from other systems in terms of the four design principles that have guided its development. Keywords Synchronous groupware, multi-user applications, group-ware infrastructure, client/server architectures, notification, protocol, design principles, performance, state sharing.