Publication statistics

Pub. period:2003-2012
Pub. count:30
Number of co-authors:54



Co-authors

Number of publications with 3 favourite co-authors:

Keith Cheverst:7
Mark Rouncefield:6
Gerd Kortuem:4

 

 

Productive colleagues

Christian Kray's 3 most productive colleagues in number of publications:

Albrecht Schmidt:111
Alan J. Dix:107
Hans-Werner Geller..:73
 
 
 

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Christian Kray

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Publications by Christian Kray (bibliography)

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2012
 
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Fechner, Thore and Kray, Christian (2012): Attacking location privacy: exploring human strategies. In: Proceedings of the 2012 International Conference on Uniquitous Computing 2012. pp. 95-98. Available online

The proliferation of location-based services in recent years has highlighted the need to consider location privacy. This has led to the development of methods enhancing location privacy, and to the investigation of reasons for sharing location information. While computational attacks on location privacy and their prevention have attracted a lot of research, attacks based on humans strategies and tactics have mostly been considered implicitly. This note addresses this knowledge gap by reporting on a user study, which we conducted in the context of a location-based game. Participants had to identify other players over the course of several weeks. The results show that human strategies for deanonymization and re-identification can be highly successful and thus pose a threat to location privacy comparable to computational attacks. By incorporating real-world knowledge (that is not easily available in automated attacks), human players were able to efficiently identify other people in the game.

© All rights reserved Fechner and Kray and/or ACM Press

2010
 
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Kray, Christian, Nesbitt, Daniel, Dawson, John and Rohs, Michael (2010): User-defined gestures for connecting mobile phones, public displays, and tabletops. In: Proceedings of 12th Conference on Human-computer interaction with mobile devices and services 2010. pp. 239-248. Available online

Gestures can offer an intuitive way to interact with a computer. In this paper, we investigate the question whether gesturing with a mobile phone can help to perform complex tasks involving two devices. We present results from a user study, where we asked participants to spontaneously produce gestures with their phone to trigger a set of different activities. We investigated three conditions (device configurations): phone-to-phone, phone-to-tabletop, and phone to public display. We report on the kinds of gestures we observed as well as on feedback from the participants, and provide an initial assessment of which sensors might facilitate gesture recognition in a phone. The results suggest that phone gestures have the potential to be easily understood by end users and that certain device configurations and activities may be well suited for gesture control.

© All rights reserved Kray et al. and/or their publisher

 
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Doering, Tanja, Pfleging, Bastian, Kray, Christian and Schmidt, Albrecht (2010): Design by physical composition for complex tangible user interfaces. In: Proceedings of ACM CHI 2010 Conference on Human Factors in Computing Systems 2010. pp. 3541-3546. Available online

In this paper, we present a novel approach to create devices with tangible user interfaces by physical com-position. While the separation of the user interface from the application logic has a long tradition in software engineering, for products with tangible user interfaces there is no equivalent approach that realizes a true separation and flexible combination of interface components, underlying technology, and software parts. We propose a novel concept that is based on an inner Core for the basic technical and software platform of a product and an outer Shell that builds a flexible and ex-changeable tangible user interface from passive components. Using vision-based tracking, we can realize a clear separation between the components. No wiring is necessary. This paper introduces our novel approach and presents a first working prototype as well as initial results from its application in a design workshop.

© All rights reserved Doering et al. and/or their publisher

2009
 
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Snowdon, Caroline and Kray, Christian (2009): Exploring the use of landmarks for mobile navigation support in natural environments. In: Proceedings of 11th Conference on Human-computer interaction with mobile devices and services 2009. p. 13. Available online

Landmarks are a key element in navigation and have been used extensively to provide navigation support to pedestrians through mobile devices in urban areas. Natural environments differ significantly from built environments in a number of ways including, for example, the degree of structure and regularity, the types and density of landmarks, and the way in which people navigate in those environments. In this paper, we investigate how people currently navigate 'in the wild', and whether landmark-based navigation support through mobile devices is a feasible option in such settings. We present results from two studies: a questionnaire-based study focussing on current practice and the use of landmarks, and a qualitative lab-based study using immersive panoramic photographs and photographs of (natural) landmarks investigating the feasibility of landmark-based navigation support in natural environments. The results indicate that a small number of means are currently used for navigation in the wild, and that certain types of landmarks might be feasible for navigation support on mobile devices. We also found initial evidence that immersive panoramic photographs may constitute a promising way to evaluate mobile applications.

© All rights reserved Snowdon and Kray and/or their publisher

 
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Kray, Christian, Rohs, Michael, Hook, Jonathan and Kratz, Sven (2009): Bridging the gap between the Kodak and the Flickr generations: A novel interaction technique for collocated photo sharing. In International Journal of Human-Computer Studies, 67 (12) pp. 1060-1072. Available online

Passing around stacks of paper photographs while sitting around a table is one of the key social practices defining what is commonly referred to as the 'Kodak Generation'. Due to the way digital photographs are stored and handled, this practice does not translate well to the 'Flickr Generation', where collocated photo sharing often involves the (wireless) transmission of a photo from one mobile device to another. In order to facilitate 'cross-generation' sharing without enforcing either practice, it is desirable to bridge this gap in a way that incorporates familiar aspects of both. In this paper, we discuss a novel interaction technique that addresses some of the constraints introduced by current communication technology, and that enables photo sharing in a way, which resembles the passing of stacks of paper photographs. This technique is based on dynamically generated spatial regions around mobile devices and has been evaluated through two user studies. The results we obtained indicate that our technique is easy to learn and as fast, or faster than, current technology such as transmitting photos between devices using Bluetooth. In addition, we found evidence of different sharing techniques influencing social practice around photo sharing. The use of our technique resulted in a more inclusive and group-oriented behavior in contrast to Bluetooth photo sharing, which resulted in a more fractured setting composed of sub-groups.

© All rights reserved Kray et al. and/or Academic Press

 
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Siek, Katie A., Neely, Steve, Stevenson, Graeme, Kray, Christian and Mulder, Ingrid (2009): Guest Editorial Preface Advances in Evaluating Mobile and Ubiquitous Systems. In International Journal of Mobile Human Computer Interaction, 1 (2) pp. i-x. Available online

2008
 
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Kray, Christian, Rohs, Michael, Hook, Jon and Kratz, Sven G. (2008): Group coordination and negotiation through spatial proximity regions around mobile devices on augmented tabletops. In: Third IEEE International Workshop on Tabletops and Interactive Surfaces Tabletop 2008 October 1-3, 2008, Amsterdam, The Netherlands. pp. 1-8. Available online

 
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Kray, Christian, Cheverst, Keith, Harrison, Michael D., Hamhoum, Fathi and Wagner, Jrgen (2008): Towards a location model for indoor navigation support through public displays and mobile devices. In: Henze, Niels, Broll, Gregor, Rukzio, Enrico, Rohs, Michael, Zimmermann, Andreas and Boll, Susanne (eds.) Mobile Interaction with the Real World 2008 - MIRW 2008 - Mobile HCI Workshop September 2, 2008, Amsterdam, The Netherland. pp. 83-92. Available online

 
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Connelly, Kay, Siek, Katie A., Mulder, Ingrid, Neely, Steve, Stevenson, Graeme and Kray, Christian (2008): Evaluating Pervasive and Ubiquitous Systems. In IEEE Pervasive Computing, 7 (3) pp. 85-88. Available online

 
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Mller, Jorg, Jentsch, Marc, Kray, Christian and Krger, Antonio (2008): Exploring factors that influence the combined use of mobile devices and public displays for pedestrian navigation. In: Proceedings of the Fifth Nordic Conference on Human-Computer Interaction 2008. pp. 308-317. Available online

Large displays are rapidly proliferating in public spaces, and could therefore be an attractive resource to support nomadic users in such contexts, e. g. by providing additional screen real estate or by augmenting services delivered through a mobile device. While previous work on combining public displays and mobile devices has identified a number of benefits of this combination, it is not yet clear if users will actually use such a system and if they do, why and when. In this paper, we present two initial user studies investigating factors relevant to user acceptance and usability in the context of a deployed system that provides pedestrian navigation support through a combination of mobile devices and public displays. Based on the results from a repertory grid analysis, we identify dimensions that are relevant for users deciding whether to use a public display or not, and discuss implications for the design of such systems.

© All rights reserved Mller et al. and/or their publisher

2006
 
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Butz, Andreas, Kray, Christian, Kruger, Antonio and Schwesig, Carsten (2006): Workshop W2: multi-user and ubiquitous user interfaces (MU3I 2006). In: Proceedings of the 2006 International Conference on Intelligent User Interfaces 2006. p. 15. Available online

The main objective of the third workshop on Multi-User and Ubiquitous User Interfaces (MU3I 2006) is to bring people with relevant backgrounds (e.g. interface design, CSCW, ubiquitous computing) together to discuss two key questions in this field: How can we build interfaces, which span multiple devices so that the user knows that they can be used to control a specific application? How can we build interfaces for public displays? Therefore, the main outcome of the workshop is expected to consists of further insights into those problems, potential solutions and a research agenda to investigate these further.

© All rights reserved Butz et al. and/or ACM Press

 
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Kray, Christian, Cheverst, Keith, Fitton, Dan, Sas, Corina, Patterson, John F., Rouncefield, Mark and Stahl, Christoph (2006): Sharing control of dispersed situated displays between nand residential users. In: Proceedings of 8th conference on Human-computer interaction with mobile devices and services 2006. pp. 61-68. Available online

As the number of public displays in the environment increases, new opportunities open up to improve situated interaction and to enable new kinds of applications. In order to make distributed display resources available to nomadic users, a key issue to address is how control can be dynamically shared between display users. It is important to study how control over a shared display can be acquired, released or shared by nomadic and residential users given their competing demands for display resources. In this paper, we present a system and a user study investigating these issues in the context of two applications both competing for display resources provided by a deployment of interactive office doorplates. The first application (Hermes II) provides situated note leaving and messaging services whereas the second one (GAUDI) supports user navigating a university department. Office occupants (i.e., residential users) can control whether the navigation application may (temporarily) use their doorplate display (thus giving priority to the navigation needs of nomadic users to the department). We report on findings from a user study, and discuss interface design implications for specifying display control.

© All rights reserved Kray et al. and/or ACM Press

 
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Singh, Pushpendra, Ha, Hai Nam, Kuang, Zhiwen, Olivier, Patrick, Kray, Christian, Blythe, Phil and James, Phil (2006): Immersive video as a rapid prototyping and evaluation tool for mobile and ambient applications. In: Proceedings of 8th conference on Human-computer interaction with mobile devices and services 2006. p. 264. Available online

A key issue in mobile and ambient computing is the effort required to rapidly prototype and evaluate user interfaces and applications. Existing technologies for these tasks suffer either from low fidelity (e.g. paper prototypes, mental walkthroughs) or effectively require a near full-scale deployment. We propose an approach using immersive video with surround sound and a simulated infrastructure to create a very realistic environment in the office or the lab. It provides a low-cost and rapid means to prototype user interfaces and applications, and to evaluate them in a realistic simulation of the context, in which they are intended to be used.

© All rights reserved Singh et al. and/or ACM Press

 
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Kray, Christian, Cheverst, Keith, Fitton, Dan, Sas, Corina, Patterson, John, Rouncefield, Mark and Stahl, Christoph (2006): Sharing control of dispersed situated displays between nand residential users. In: Nieminen, Marko and Roykkee, Mika (eds.) Proceedings of the 8th Conference on Human-Computer Interaction with Mobile Devices and Services - Mobile HCI 2006 September 12-15, 2006, Helsinki, Finland. pp. 61-68. Available online

 
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Singh, Pushpendra, Ha, Hai Nam, Kwang, Zhiwen, Olivier, Patrick, Kray, Christian, Blythe, Phil and James, Phil (2006): Immersive video as a rapid prototyping and evaluation tool for mobile and ambient applications. In: Nieminen, Marko and Roykkee, Mika (eds.) Proceedings of the 8th Conference on Human-Computer Interaction with Mobile Devices and Services - Mobile HCI 2006 September 12-15, 2006, Helsinki, Finland. p. 264. Available online

2005
 
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Kortuem, Gerd, Kray, Christian and Gellersen, Hans-Werner (2005): Sensing and visualizing spatial relations of mobile devices. In: Proceedings of the 2005 ACM Symposium on User Interface Software and Technology 2005. pp. 93-102. Available online

Location information can be used to enhance interaction with mobile devices. While many location systems require instrumentation of the environment, we present a system that allows devices to measure their spatial relations in a true peer-to-peer fashion. The system is based on custom sensor hardware implemented as USB dongle, and computes spatial relations in real-time. In extension of this system we propose a set of spatialized widgets for incorporation of spatial relations in the user interface. The use of these widgets is illustrated in a number of applications, showing how spatial relations can be employed to support and streamline interaction with mobile devices.

© All rights reserved Kortuem et al. and/or ACM Press

 
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Kray, Christian and Baus, Jorg (2005): AIMS 2005: artificial intelligence in mobile systems. In: Proceedings of 7th conference on Human-computer interaction with mobile devices and services 2005. pp. 353-354. Available online

AIMS 2005 is the sixth workshop in a series of events that investigate various topics at the intersection of applied artificial intelligence and mobile computing. The main goal of this year's workshop is to discuss AI methods and approaches that enable adaptive and intelligent user interfaces in a mobile setting. Relevant topics include (but are not limited to) context awareness, resource adaptation and interaction metaphors in mobile and/or ubiquitous systems. The workshop combines technical presentations with focussed discussion to drive interaction between participants.

© All rights reserved Kray and Baus and/or ACM Press

 
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Graham, Connor, Cheverst, Keith, Rouncefield, Mark and Kray, Christian (2005): Going more public: situated display design in a care setting through co-realisation. In: Proceedings of the Conference on Designing for User Experiences DUX05 2005. p. 18. Available online

We describe findings from field work at a residential community care facility for ex-psychiatric hospital patients. The field work focused on distributed care-workers who looked after residents at the two sites forming the facility. We reflect on the process of co-realisation that verified our understanding of the setting and generated initial technology designs. This involved sharing scenarios descriptive of typical activity with care workers and presenting a demonstration of networked public display technology in use. We then illustrate how co-realisation both refined our understanding of care workers' work needs and informed us about how and where public display technology could be deployed. Finally, we present an initial design for a public display.

© All rights reserved Graham et al. and/or ACM Press

 
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Butz, Andreas, Kray, Christian, Krger, Antonio, Schmidt, Albrecht and Prendinger, Helmut (eds.) Proceedings of the 2nd Workshop on Multi-User and Ubiquitous User Interfaces MU3I January 9, 2005, San Diego, USA.

 
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Cheverst, Keith, Dix, Alan J., Fitton, Daniel, Kray, Christian, Rouncefield, Mark, Sas, Corina, Saslis-Lagoudakis, George and Sheridan, Jennifer G. (2005): Exploring bluetooth based mobile phone interaction with the hermes photo display. In: Tscheligi, Manfred, Bernhaupt, Regina and Mihalic, Kristijan (eds.) Proceedings of the 7th Conference on Human-Computer Interaction with Mobile Devices and Services - Mobile HCI 2005 September 19-22, 2005, Salzburg, Austria. pp. 47-54. Available online

 
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Kray, Christian and Baus, Jorg (2005): AIMS 2005: artificial intelligence in mobile systems. In: Tscheligi, Manfred, Bernhaupt, Regina and Mihalic, Kristijan (eds.) Proceedings of the 7th Conference on Human-Computer Interaction with Mobile Devices and Services - Mobile HCI 2005 September 19-22, 2005, Salzburg, Austria. pp. 353-354. Available online

 
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Cheverst, Keith, Dix, Alan J., Fitton, Dan, Kray, Christian, Rouncefield, Mark, Saslis-Lagoudakis, George and Sheridan, Jennifer G. (2005): Exploring Mobile Phone Interaction with Situated Displays. In: Rukzio, Enrico, Hkkil, Jonna, Spasojevic, Mirjana, Mntyjrvi, Jani and Ravi, Nishkam (eds.) PERMID 2005 - Pervasive Mobile Interaction Devices - Mobile Devices as Pervasive User Interfaces and Interaction Devices - Workshop in conjunction with The 3rd International Conference on Pervasive Computing PERVASIVE 2005 May 11, 2005, Munich, Germany. pp. 43-47. Available online

 
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Fitton, Daniel, Cheverst, Keith, Kray, Christian, Dix, Alan J., Rouncefield, Mark and Saslis-Lagoudakis, George (2005): Rapid prototyping and user-centered design of interactive display-based systems. In IEEE Pervasive Computing, 4 (4) pp. 58-66. Available online

2004
 
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Butz, Andreas, Kruger, Antonio, Kray, Christian and Schmidt, Albrecht (2004): Workshop W5: multi-user and ubiquitous user interfaces (MU3I). In: Nunes, Nuno Jardim and Rich, Charles (eds.) International Conference on Intelligent User Interfaces 2004 January 13-16, 2004, Funchal, Madeira, Portugal. pp. 378-379. Available online

The workshop on Multi-User and Ubiquitous User Interfaces (MU3I) discusses examples of and principles underlying user interfaces for ubiquitous computing and multi-user interfaces. It raises issues such as interface adaptation, resource limitations, and novel interaction techniques. The workshop is held as a full day event and the papers were reviewed by an international program committee. Online proceedings are available at http://www.mu3i.org/.

© All rights reserved Butz et al. and/or ACM Press

 
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Kray, Christian and Kortuem, Gerd (2004): Interactive Positioning Based on Object Visibility. In: Brewster, Stephen A. and Dunlop, Mark D. (eds.) Mobile Human-Computer Interaction - Mobile HCI 2004 - 6th International Symposium September 13-16, 2004, Glasgow, UK. pp. 276-287. Available online

 
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Strohbach, Martin, Gellersen, Hans-Werner, Kortuem, Gerd and Kray, Christian (2004): Cooperative Artefacts: Assessing Real World Situations with Embedded Technology. In: Davies, Nigel, Mynatt, Elizabeth D. and Siio, Itiro (eds.) UbiComp 2004 Ubiquitous Computing 6th International Conference September 7-10, 2004, Nottingham, UK. pp. 250-267. Available online

 
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Strohbach, Martin, Kortuem, Gerd, Gellersen, Hans-Werner and Kray, Christian (2004): Using Cooperative Artefacts as Basis for Activity Recognition. In: Markopoulos, Panos, Eggen, Berry, Aarts, Emile H. L. and Crowley, James L. (eds.) EUSAI 2004 - Ambient Intelligence - Second European Symposium November 8-11, 2004, Eindhoven, The Netherlands. pp. 49-60. Available online

2003
 
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Kray, Christian, Elting, Christian, Laakso, Katri and Coors, Volker (2003): Presenting route instructions on mobile devices. In: Johnson, Lewis and Andre, Elisabeth (eds.) International Conference on Intelligent User Interfaces 2003 January 12-15, 2003, Miami, Florida, USA. pp. 117-124. Available online

In this paper, we evaluate several means of presenting route instructions to a mobile user. Starting from an abstract language-independent description of a route segment, we show how to generate various presentations for a mobile device ranging from spoken instructions to 3D visualizations. We then examine the relationship between the quality of positional information, available resources and the different types of presentations. The paper concludes with guidelines that help to determine which presentation to choose for a given situation.

© All rights reserved Kray et al. and/or ACM Press

 
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Laakso, Katri and Kray, Christian (2003): TellMaris and deep map: two navigational assistants. In: Johnson, Lewis and Andre, Elisabeth (eds.) International Conference on Intelligent User Interfaces 2003 January 12-15, 2003, Miami, Florida, USA. p. 324. Available online

This demo will present Tellmaris and Deep Map, two system offering navigational assistance and other services to an untrained user. We will put an emphasis on different ways to present route instructions on mobile devices.

© All rights reserved Laakso and Kray and/or ACM Press

 
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Kray, Christian, Krger, Antonio and Endres, Christoph (2003): Some Issues on Presentations in Intelligent Environments. In: Aarts, Emile H. L., Collier, Ren, Loenen, Evert van and Ruyter, Boris E. R. de (eds.) EUSAI 2003 - Ambient Intelligence - First European Symposium November 3-4, 2003, Veldhoven, The Netherlands. pp. 15-26. Available online

 
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