Mark Weiser

Some computer science issues in ubiquitous computing

Ubiquitous computing is the method of enhancing computer use by making many computers available throughout the physical environment, but making them effectively invisible to the user. Since we started this work at Xerox PARC in 1988, a number of researchers around the world have begun to work in the ubiquitous computing framework. This paper explains what is new and different about the computer science in ubiquitous computing. It starts with a brief overview of ubiquitous computing, and then elaborates through a series of examples drawn from various subdisciplines of computer science: hardware components (e.g. chips), network protocols, interaction substrates (e.g. software for screens and pens), applications, privacy, and computational methods. Ubiquitous computing offers a framework for new and exciting research across the spectrum of computer science.

Scheduling for reduced CPU energy

The energy usage of computer systems is becoming more important, especially for battery operated systems. Displays, disks, and cpus, in that order, use the most energy. Reducing the energy used by displays and disks has been studied elsewhere; this paper considers a new method for reducing the energy used by the cpu. We introduce a new metric for cpu energy performance, millions-of-instructions-per-joule (MIPJ). We examine a class of methods to reduce MIPJ that are characterized by dynamic control of system clock speed by the operating system scheduler. Reducing clock speed alone does not reduce MIPJ, since to do the same work the system must run longer. However, a number of methods are available for reducing energy with reduced clock-speed, such as reducing the voltage [Chandrakasan et al 1992][Horowitz 1993] or using reversible [Younis and Knight 1993] or adiabatic logic [Athas et al 1994].n What are the right scheduling algorithms for taking advantage of reduced clock-speed, especially in the presence of applications demanding ever more instructions-per-second? We consider several methods for varying the clock speed dynamically under control of the operating system, and examine the performance of these methods against workstation traces. The primary result is that by adjusting the clock speed at a fine grain, substantial CPU energy can be saved with a limited impact on performance.

The computer for the 21 st century

[This article is unavailable due to copyright restrictions.] Specialized elements of hardware and software, connected by wires, radio waves and infrared, will soon be so ubiquitous that no-one will notice their presence.

The coming age of calm technolgy

The important waves of technological change are those that fundamentally alter the place of technology in our lives. What matters is not technology itself, but its relationship to us.

Garbage collection in an uncooperative environment

We describe a technique for storage allocation and garbage collection in the absence of significant co‐operation from the code using the allocator. This limits garbage collection overhead to the time actually required for garbage collection. In particular, application programs that rarely or never make use of the collector no longer encounter a substantial performance penalty. This approach greatly simplifies the implementation of languages supporting garbage collection. It further allows conventional compilers to be used with a garbage collector, either as the primary means of storage reclamation, or as a debugging tool.

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 origins of ubiquitous computing research at PARC in the late 1980s

Ubiquitous computing began in the Electronics and Imaging Laboratory of the Xerox Palo Alto Research Center. This essay tells the inside story of its evolution from “computer walls” to “calm computing.”

The computer for the 21st Century

Specialized elements of hardware and software, connected by wires, radio waves and infrared, will soon be so ubiquitous that no-one will notice their presence.

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.

The future of ubiquitous computing on campus

cated that staffing was critical, and that the combination of a place for them to work and a full-time staff member on hand to help them with both the planning and the small vexations was what it took to complete their projects. Enough has been written about the support crisis in academic technology that it is easier for administrators to understand the need for staffing. In this case, the cost of dedicating a full-time staff member to supporting faculty development should be looked at in the context of the whole faculty and the whole curriculum. In that context, an incremental cost of less than 1% provides far more than that amount in benefits. The final chapter in our faculty development effort is not yet written, but the ability to reach a greater proportion of the faculty this year, together with the earlier programs for access and academic facilities appears to be finally working to produce the desired result.