This essay considers the problem of defining the context that context aware systems should pay attention to from a human perspective. In particular, we argue that there are human aspects of context that cannot be sensed or even inferred by technological means, so context aware systems cannot be designed simply to act on our behalf. Rather they will have to be able to defer to users in an efficient and non-obtrusive fashion. Our point is particularly relevant for systems that are constructed such that applications are architecturally isolated from the sensing and inferencing that governs their behavior. We propose a design framework that is intended to guide thinking about accommodating human aspects of context. This framework presents four design principles that support intelligibility of system behavior and accountability of human users and a number of human-salient details of context that must be accounted for in context aware system design.

Mobile urban environments present a challenge for context-aware computers because they differ from fixed indoor contexts such as offices, meeting rooms, and lecture halls in many important ways. Internal factors such as tasks and goals are different---external factors such as social resources are dynamic and unpredictable. An empirical, user-centred approach is needed to understand mobile contexts. In this paper, we present insights from an ethnomethodologically inspired study of 25 adult urbanites in Helsinki. The results describe typical phenomena in mobility: how situational and planned acts intermesh in navigation, how people construct personal and group spaces, and how temporal tensions develop and dissolve. Furthermore, we provide examples of social solutions to navigation problems, examine mobile multitasking, and consider design implications for mobile and context-aware human-- computer interaction.

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Abstract. The meaning of context with respect to computational systems has been the focus of considerable discussion specifically as related to context aware and proactive computing. However, there are no reports of people’s direct, experiential understanding of the “lived experience ” of context. As a result, there is a significant gap between theoretical approaches for understanding context and the actual practice of context, which is critical for the specification of systems. This paper reports the results of an ethnographic case study that illuminates the practical nature of context and highlights specific challenges for ubiquitous computing systems in general. We conclude that context is simultaneously more subtle, fluid and idiosyncratic than previously reported under theoretical approaches to understanding context. We further suggest implications for the design of computing systems based on these findings. 1

This paper presents the approach and the outcome of a study, called Where’s-the-phone to identify characteristics of how mobile phones are carried whilst users are out and about in public spaces. A series of contextual interviews were conducted in public spaces of Helsinki, Milan and New York collecting 419 responses in total. The results show a strong tendency by gender, with females using bags and males using trouser pockets to place their mobile phones. Comments from participants suggested users did not place the phone wherever available, but rather considered many aspects, such as the convenience, tolerance to multiple postures, risk of theft, comfort, or impact to their appearance. We learnt that bag users miss incoming alerts more often than with other carrying methods. Based on the outcome of the study, we discuss the challenges in designing mobile devices, in particular mobile phones. Keywords Mobile context, handheld computing, mobile phone, contextual interview, device location

For automatic or context-aware systems a major issue is user trust, which is to a large extent determined by system reliability. For systems based on sensor input which are inherently uncertain or even uncomplete there is little hope that they will ever be perfectly reliable. In this paper we test the hypothesis if explicitly displaying the current confidence of the system increases the usability of such systems. For the example of a context-aware mobile phone, the experiments show that displaying confidence information increases the user’s trust in the system.

Social context is an important yet an underresearched area in context-sensitive computing. This paper adopts a framework from social sciences that views social context as a sequence of turns taken between participants. The approach is illustrated and evaluated through three empirical cases. The results show that social context is not a static and passive surrounding of a device, but dynamic and constructed by people. Challenges and restrictions for modeling social context through turntaking are identified.

In this paper, we develop a theoretical understanding of multi-sensory knowledge and user context and their interrelationships. This is used to develop a generic representation framework for multi-sensory knowledge and context. A representation framework for context can have a significant impact on media applications that dynamically adapt to user needs. There are three key contributions of this work: (a) theoretical analysis, (b) representation framework and (c) experimental validation. Knowledge is understood to be a dynamic set of multi-sensory facts with three key properties – multi-sensory, emergent and dynamic. Context is the dynamic subset of knowledge that affects the communication between entities. We develop a graph based, multi-relational representation framework for knowledge, and model its temporal using a linear dynamical system. Our approach results in a stable and convergent system. We applied our representation framework to a image retrieval system with a large collection of photographs from everyday events. Our experimental validation with against two reference algorithms indicates that our context based approach provides significant gains in real-world usage scenarios.

Information appliances, user interfaces, and context-aware devices are necessarily based on approximations of potential users and usage situations. However, it is not an unusual experience for developers that in some areas, appropriate approximations are extremely difficult to realize. Often, these difficulties are not apparent from the beginning. Nevertheless, difficulties are rarely addressed in the pervasive computing literature as they appear to be peripheral compared to the technical challenges. In this paper, we argue that the field would largely benefit from addressing these issues explicitly. First, focussed discussions would help identify areas that have already shown to be difficult or even intractable in related disciplines, such as AI or CSCW. Second, it would help developers become aware of the difficulties and would allow them to deliberately circumvent such areas. We use example scenarios from the pervasive computing literature to illustrate these points. Difficulties to describe and to analyze impacts of pervasive computing applications indicate a need for an analysis framework providing a specific terminology.

Abstract. Many existing localization systems generate location predictions, but fail to report how accurate the predictions are. This paper explores the effect of revealing the error of location predictions to the end-user in a location finding field study. We report findings obtained under four different error visualization conditions and show significant benefit in revealing the error of location predictions to the user in location finding tasks. We report the observed influences of error on participants’ strategies for location finding. Additionally, given the observed benefit of a dynamic estimate of error, we design practical algorithms for estimating the error of a location prediction. Analysis of the algorithms shows a median estimation inaccuracy of up to 50m from the predicted location’s true error. 1