Introduction

In the last decade, computers connecting with humans and vice versa have increased the importance of human–computer interaction (HCI) more than ever in society. In the early days of computing, when computers occupied a whole room and required huge cooling fans, programmers and mathematicians were their main users. In the late 1970s and early 1980s, Doug Engelbart’s “Mother of all Demos”1 changed society’s concept of computers, showcasing for the first time the desktop environment metaphor, including the use of a mouse, a window-based graphical interface, and hypertext. Engelbart’s vision transformed computers into essential office equipment, where those who were not-so-tech-savvy and people with no computer science knowledge were the main users [Shackel 1997]. The prob­ lem of usability became more significant when computers escaped the office envi­ ronment and found their ways to personal spaces [Thacker et al. 1979]. As predicted by Mark Weiser in [1999], “The Computer for The 21st Century” is transformed from desktop forms to invisible, sensor-enabled, and intelligent entities sharing the same space as humans everywhere, hence the user groups are widened. This transformation is supported by, and driven by both technical innovations such as interconnectivity via high-speed wireless networks, fast multi-core embedded pro­ cessors, high-capacity fast-charging batteries, embedded high-precision sensors, and new interaction methods, such as the touchscreen, gesturing, and speechbased conversational interfaces. Despite this rapid progress in engineering, which has afforded all the necessary components for Weiser’s vision of ubiquitous com­ puting, our understanding of how these user groups of unprecedented broadness can, do, or should interact with these diverse and ubiquitous computers, is trail­ ing our engineering achievements. HCI researchers and practitioners need to be able to make sense of the rich and heterogeneous stream of data that emerges dur­ ing interaction with ubiquitous computers, in order to craft the new paradigms