Bill N. Schilit

Context-Aware Computing Applications

This paper describes systems that examine and react to an individuals changing context. Such systems can promote and mediate peoples interactions with devices, computers, and other people, and they can help navigate unfamiliar places. We believe that a limited amount of information covering a persons proximate environment is most important for this form of computing since the interesting part of the world around us is what we can see, hear, and touch. In this paper we define context-aware computing, and describe four catagories of context-aware applications: proximate selection, automatic contextual reconfiguration, contextual information and commands, and contex-triggered actions. Instances of these application types have been prototyped on the PARCTAB, a wireless, palm-sized computer.

An overview of the PARCTAB ubiquitous computing experiment

The PARCTAB system integrates a palm-sized mobile computer into an office network. The PARCTAB project serves as a preliminary testbed for ubiquitous computing, a philosophy originating at Xerox PARC that aims to enrich our computing environment by emphasizing context sensitivity, casual interaction and the spatial arrangement of computers. This article describes the ubiquitous computing philosophy, the PARCTAB system, user interface issues for small devices, and our experience in developing and testing a variety of mobile applications.

The PARCTAB mobile computing system

The PARCTAB is a personal digital assistant (PDA) that communicates via infrared (IR) datapackets to a network of IR transceivers. The infrared network is designed for in-building use, where each room becomes a communication cell. In contrast to the approach used by other PDAs, most PARCTAB applications run on remote hosts and therefore depend on reliable communication through the IR network. The infrastructure provides reliability as well as uninterrupted service when a PARCTAB moves from cell to cell. The PARCTAB and a supporting infrastructure has been operational since March 1993 at the Computer Science Lab at Xerox PARC. The system currently comprises thirty cells and twenty-five PARCTABs and will expand in the near future. There are three types of software components in the PARCTAB system: gateways, agents, and applications. Gateways implement a datagram service for sending and receiving packets using IR signals. Each tab is represented by an agent. An agent tracks the location of its tab and provides location independent reliable remote procedure calls. The protocols enforce security, preventing, for example, an unauthorized application from taking control of a tab.<<ETX>>

The Parctab Ubiquitous Computing Experiment

The ParcTab system integrates a palm-sized mobile computer into an office network. This project serves as a preliminary testbed for Ubiquitous Computing, a philosophy originating at Xerox PARC that aims to enrich our computing environment by emphasizing context sensitivity, casual interaction and the spatial arrangement of computers. This paper describes the Ubiquitous Computing philosophy, the ParcTab system, user-interface issues for small devices, and our experience developing and testing a variety of mobile applications.

TeleWeb: loosely connected access to the World Wide Web

Abstract The development of the World Wide Web (WWW) has made people reliant on continuous, high-speed, low-cost networks in order to get work done. Ideally, one should be able to browse the Web anytime, anywhere, whether connected to such a network or not. This paper describes the design of TeleWeb, a system we are building to support this goal. We believe that fine-grained cost control is crucial and have developed a “reactive architecture” that supports user-specified adaptation under various operating conditions. There are four key features to TeleWebs architecture: costs are made visible to the user through annotated HTML; budget monitoring warns the user when operations exceed pre-specified limits; actions may be postponed and later triggered when conditions are met; and finally, user customization and system configuration values may automatically adapt according to the changing conditions of use. These mechanisms work together to provide an asynchronous, email-style of browsing in which users can work disconnected from a cache of documents, or trade off communication cost against information needs.

Expanding the horizons of location-aware computing

Thanks to technical progress on many fronts, we now have location-aware computer applications that sense their location and modify their settings, user interface, and functions accordingly.