Toward Design Principles for Invisible Interfaces Mark D. Gross Design Machine Group University of Washington Seattle WA 98195-5720 001-206-616-2817 mdgross@u.washington.edu Ellen Yi-Luen Do Design Machine Group University of Washington Seattle WA 98195-5720 001-206-616-2816 ellendo@u.washington.edu ABSTRACT An important and long-standing goal of interaction design is to make interfaces invisible. Effective interaction design in embodied computing must map the inputs and outputs of the computational process with the qualities of the physical artifact in which it is embedded, taking into account qualities such as size, shape, texture, material, and geometry. To go beyond ad- hoc demonstration projects, style guides, pattern languages, and toolkits, a principled approach to designing embodied interaction is needed. We present in this paper a collection of physical computing projects that leverages our understanding of physicality of objects and describe principles and classifications that link them together. Categories and Subject Descriptors H.5.2 [Information Interfaces and Presentation]: User Interfaces – evaluation/methodology, haptic I/O, interaction styles, style guides, theory and methods General Terms Design, Human Factors, Languages, Theory Keywords tangible, physical, design method. 1. COMPUTATIONAL AND PHYSICAL DESIGN As computation moves beyond the screen into the physical world we inhabit, the dimensions of interaction design expand to include the domain of industrial designers and architects. Effective design of embodied computational systems depends on understanding, then mapping, their physical and computational characteristics. Many are now developing artifacts that employ tangible interaction, mixed and augmented reality, ubiquitous computing. These first generation, ad-hoc one-off investigations are novel and intriguing and they indicate a rich and large universe of possible designs. How can we understand the relationships between the physical and computational characteristics of these hybrid systems? Can we develop more systematic ways of making design decisions? 1.1 Real “direct manipulation” Over the twenty-five years in which windows–mouse–menu interaction has dominated, users have developed expectations for screen-based interaction and accordingly, guidelines for the appropriate design of screen based computational artifacts. These are codified in UI guidelines, accessibility standards, and conventional wisdom and prejudice. However, little of this is useful when designing physically embedded computational artifacts. In the heyday of the mouse-menu interaction paradigm, Schneiderman coined the term “direct manipulation,” in which users select screen objects with a mouse and edit them or apply operations to them with tools chosen from a nearby palette. Yet compared to, for example, a pen-based drawing environment where one simply draws what one wants, a mouse-menu interface to a draw program seemed a terribly indirect way to manipulate the objects in one’s world. Today we are on the threshold of real direct manipulation. The objects you manipulate in the physical world are the objects themselves, not graphical depictions of them. Physicality is a sort of meta- interface and the mapping of a physical object to a task is often more obvious than mapping of a menu to that task. Endowing physical objects with computational capabilities allows a rich interaction without the traditional GUI trappings such as menus—an invisible interaction. 1.2 Invisibility and the fabric of life We look to the history of technology to see how innovations such as books and recorded music, central heat, electric light, and the telephone were designed, redesigned, and gradually assimilated. Each of these examples has physical embodiments (the size, shape, typefaces of books; the controls and ductwork of central heat; the switches, fixtures, and cabling of electric light). Initially novel and therefore glaringly obvious, for the most part we have now incorporated these embodiments into the actions and rituals of our lives. An interface becomes invisible when we stop noticing it; as a technology becomes commonplace it fades into the fabric of life. Permission to make digital or hard copies of all or part of this work for personal or classroom use is granted without fee provided that copies are not made or distributed for profit or commercial advantage and that copies bear this notice and the full citation on the first page. To copy otherwise, or republish, to post on servers or to redistribute to lists, requires prior specific permission and/or a fee. Conference’04, Month 1–2, 2004, City, State, Country. Copyright 2004 ACM 1-58113-000-0/00/0004…$5.00.