Vassilis Kostakos

Instrumenting the city: developing methods for observing and understanding the digital cityscape

We approach the design of ubiquitous computing systems in the urban environment as integral to urban design. To understand the city as a system encompassing physical and digital forms and their relationships with peoples behaviours, we are developing, applying and refining methods of observing, recording, modelling and analysing the city, physically, digitally and socially. We draw on established methods used in the space syntax approach to urban design. Here we describe how we have combined scanning for discoverable Bluetooth devices with two such methods, gatecounts and static snapshots. We report our experiences in developing, field testing and refining these augmented methods. We present initial findings on the Bluetooth landscape in a city in terms of patterns of Bluetooth presence and Bluetooth naming practices.

An Assessment of Intrinsic and Extrinsic Motivation on Task Performance in Crowdsourcing Markets

Crowdsourced labor markets represent a powerful new paradigm for accomplishing work. Understanding the motivating factors that lead to high quality work could have significant benefits. However, researchers have so far found that motivating factors such as increased monetary reward generally increase workers’ willingness to accept a task or the speed at which a task is completed, but do not improve the quality of the work. We hypothesize that factors that increase the intrinsic motivation of a task – such as framing a task as helping others – may succeed in improving output quality where extrinsic motivators such as increased pay do not. In this paper we present an experiment testing this hypothesis along with a novel experimental design that enables controlled experimentation with intrinsic and extrinsic motivators in Amazon’s Mechanical Turk, a popular crowdsourcing task market. Results suggest that intrinsic motivation can indeed improve the quality of workers’ output, confirming our hypothesis. Furthermore, we find a synergistic interaction between intrinsic and extrinsic motivators that runs contrary to previous literature suggesting “crowding out” effects. Our results have significant practical and theoretical implications for crowd work.

Multipurpose Interactive Public Displays in the Wild: Three Years Later

Extended research on interactive public displays deployed in a city center reveals differences between the publics stated information needs and their actual information behavior and highlights effects that an artificial environment cannot duplicate.

rfid in pervasive computing: State-of-the-art and outlook

rfid has already found its way into a variety of large scale applications and arguably it is already one of the most successful technologies in the history of computing. Beyond doubt, rfid is an effective automatic identification technology for a variety of objects including natural, manufactured and handmade artifacts; humans and other species; locations; and increasingly media content and mobile services. In this survey we consider developments towards establishing rfid as the cost-effective technical solution for the development of open, shared, universal pervasive computing infrastructures and look ahead to its future. In particular, we discuss the ingredients of current large scale applications; the role of network services to provide complete systems; privacy and security implications; and how rfid is helping prototype emerging pervasive computing applications. We conclude by identifying common trends in the new applications of rfid and ask questions related to sustainable universal deployment of this technology.

CrisisTracker: crowdsourced social media curation for disaster awareness

Victims, volunteers, and relief organizations are increasingly using social media to report and act on large-scale events, as witnessed in the extensive coverage of the 2010-2012 Arab Spring uprisings and 2011 Japanese tsunami and nuclear disasters. Twitter® feeds consist of short messages, often in a nonstandard local language, requiring novel techniques to extract relevant situation awareness data. Existing approaches to mining social media are aimed at searching for specific information, or identifying aggregate trends, rather than providing narratives. We present CrisisTracker, an online system that in real time efficiently captures distributed situation awareness reports based on social media activity during large-scale events, such as natural disasters. CrisisTracker automatically tracks sets of keywords on Twitter and constructs stories by clustering related tweets on the basis of their lexical similarity. It integrates crowdsourcing techniques, enabling users to verify and analyze stories. We report our experiences from an 8-day CrisisTracker pilot deployment during 2012 focused on the Syrian civil war, which processed, on average, 446,000 tweets daily and reduced them to consumable stories through analytics and crowdsourcing. We discuss the effectiveness of CrisisTracker based on the usage and feedback from 48 domain experts and volunteer curators.

AWARE: Mobile Context Instrumentation Framework

We present a mobile instrumentation toolkit, AWARE, an open-source effort to develop an extensible and reusable platform for capturing, inferring, and generating context on mobile devices. Mobile phones are sensor-rich but resource-constrained, and therefore several considerations need to be addressed when creating a research tool that ensures problem-free context collection. We demonstrate how AWARE can mitigate researchers’ effort when building mobile data-logging tools and context-aware applications, with minimal battery impact. By encapsulating implementation details of sensor data retrieval and exposing the sensed context as higher-level abstractions, AWARE shifts the focus from software development to data analysis, both quantitative and qualitative. We have evaluated AWARE in several case studies and discuss its use, power consumption, and scalability.

The phone lock: audio and haptic shoulder-surfing resistant PIN entry methods for mobile devices

Tangible user interfaces are portals to digital information. In the future, securing access to such material will be an important concern. This paper describes the design, implementation and evaluation of a PIN entry system based on audio or haptic cues that is suitable for integration into such physical systems. The current implementation links movements on a mobile phone touch screen with the display of non-visual cues; selection of a sequence of these cues composes a password. Studies reveal the validity of this approach in terms of task times and error rates that improve over prior art. In sum, this paper demonstrates the potential of non-visual PINs as a mechanism for securing access to a range of systems, ultimately incorporating mobile, ubiquitous or tangible interfaces.

CHI 1994-2013: mapping two decades of intellectual progress through co-word analysis

This study employs hierarchical cluster analysis, strategic diagrams and network analysis to map and visualize the intellectual landscape of the CHI conference on Human Computer Interaction through the use of co-word analysis. The study quantifies and describes the thematic evolution of the field based on a total of 3152 CHI articles and their associated 16035 keywords published between 1994 and 2013. The analysis is conducted for two time periods (1994-2003, 2004-2013) and a comparison between them highlights the underlying trends in our community. More significantly, this study identifies the evolution of major themes in the discipline, and highlights individual topics as popular, core, or backbone research topics within HCI.

From school food to skate parks in a few clicks: using public displays to bootstrap civic engagement of the young

We present Ubinion, a service that utilizes large public interactive displays to enable young people to give personalized feedback on municipal issues to local youth workers. It also facilitates discussion and sharing the feedback online using modern social networking services. We present the motivation and rationale behind Ubinion and analyze the results from three large-scale user trials conducted in authentic settings. The evaluation shows that young users are positive about adopting Ubinion, and that they quickly appropriated its use to provide feedback outside the intended scope of the system, but still reflecting their concerns. We argue that Ubinions design as a fun and informal tool is appropriate for its purpose, and discuss the versatility of public interactive displays as a municipal feedback medium and as content sources for online communities in general.

Brief encounters: Sensing, modeling and visualizing urban mobility and copresence networks

Moving human-computer interaction off the desktop and into our cities requires new approaches to understanding people and technologies in the built environment. We approach the city as a system, with human, physical and digital components and behaviours. In creating effective and usable urban pervasive computing systems, we need to take into account the patterns of movement and encounter amongst people, locations, and mobile and fixed devices in the city. Advances in mobile and wireless communications have enabled us to detect and record the presence and movement of devices through cities. This article makes a number of methodological and empirical contributions. We present a toolkit of algorithms and visualization techniques that we have developed to model and make sense of spatial and temporal patterns of mobility, presence, and encounter. Applying this toolkit, we provide an analysis of urban Bluetooth data based on a longitudinal dataset containing millions of records associated with more than 70000 unique devices in the city of Bath, UK. Through a novel application of established complex network analysis techniques, we demonstrate a significant finding on the relationship between temporal factors and network structure. Finally, we suggest how our understanding and exploitation of these data may begin to inform the design and use of urban pervasive systems.Many complex human and natural phenomena can usefully be represented as networks describing the relationships between individuals 1,2,3,4 . While these relationships are typically intermittent, previous research has used network representations that aggregate the relationships at discrete intervals 5 . However, such an aggregation discards important temporal information, thus inhibiting our understanding of the network’s dynamic behaviour and evolution. We have recorded patterns of human urban encounter using Bluetooth technology (Figure 1) thus retaining the temporal properties of this network. Here we show how this temporal information influences the structural properties of the network. We show that the temporal properties of human urban encounter are scale-free, leading to an overwhelming proportion of brief encounters between individuals. While previous research has shown preferential attachment to result in scale-free connectivity in aggregated network data 11 , we found that scale-free connectivity results from the temporal properties of the network. In addition, we show that brief encounters act as weak social ties 6,7 in the diffusion of non-expiring information, yet persistent encounters provide the means for sustaining timeexpiring information through a network.