Proceedings of the 13th international conference on Ubiquitous computing

On behalf of the organizing committee, it is our great pleasure to welcome you to the 13th International Conference on Ubiquitous Computing. This is the third time the UbiComp conference series has come to Asia. This year's conference in Beijing, China, follows Seoul, Korea (2008) and Tokyo, Japan (2005). UbiComp is a conference that truly captures the wide variety of research activities in the diverse field of ubiquitous computing, encompassing research from, e.g., Human-Computer Interaction, Mobile Computing, Location and Sensing Technology, Machine Learning, Middleware and Systems, and Programming Models and Tools. September 2011 also marks a historic date in the history of Ubicomp. It is exactly 20 years from when Dr. Mark Weiser's historic article, "The Computer for the Twenty-First Century," appeared in Scientific American. This article is acclaimed for widely publicizing the idea of Ubicomp in the research community and setting the goals for the early years of the field. We will mark this historic occasion with a special panel in tribute to the late Dr. Weiser. Our panel of luminaries, including those who worked with Dr. Weiser at Xerox PARC, as well as his contemporaries who were influenced by his work at the time, will reminisce on Mark's predictions as well as present their view of where the field should move going forward. Each UbiComp conference represents a snapshot of our field, capturing the state-of-the-art in technology, the research challenges we are addressing, as well as the people that form the UbiComp community. Each year's proceedings represent an opportunity to learn about new areas and identify upcoming research opportunities, and this year is no exception. UbiComp 2011 continues the tradition of a single-track program that allows participants to experience the entire program in a variety of sessions, ranging from context awareness to location sharing, from home infrastructures to novel interactions, and from persuasive computing to sensing. This year our international Program Committee, composed of 28 of the leading researchers in the field, evaluated a record number of 302 submissions --- 234 full papers and 68 notes. Using a multi-phase review process, initially each submission was reviewed by at least one member of the PC and three or more external reviewers. Of the 302 submissions, 118 were evaluated by 1-2 additional PC members and discussed at a 2- day PC meeting held on the campus of the University of California, Berkeley. In total, the Program Committee and 531 external reviewers spent countless hours to provide feedback to the authors through 1343 reviews. After this rigorous process, a total of 50 submissions --- 44 full papers and 6 notes --- were accepted for publication in these proceedings, representing an overall acceptance rate of 16.6%. We feel our selective review process has resulted in a high-quality set of published papers. A sub-committee discussed and selected five of the 50 accepted papers to be recognized in these proceedings for their particular level of quality. Of these five, one stood out as the best paper of UbiComp 2011. This year also sees a high quality adjunct program, accepting 23 demos, 7 videos, and 34 posters, for a total of 56 accepted adjunct papers out of 85 submissions (note that several accepted adjunct submissions appear in multiple categories, but are only counted once in the acceptance numbers). Continued from UbiComp 2010, we encouraged authors of accepted full papers and notes to also submit a poster, video, or demo of their work, to better engage the audience and stimulate discussion. To properly reflect the significance of the work represented in the adjunct program, these submissions also see a tighter integration in the main program, with video presentations interspersed with the technical presentations of the main track, and posters and demos presented during lunch breaks. The workshop program has 13 workshops that cover both traditional Ubicomp topics (e.g., context awareness, location-based services, mobile sensing, health, and design) and newer topics (e.g., crowdsourcing and urban computing). This year, we launched the first tutorial program in UbiComp conference history. We offered five tutorials by leading experts on the topics of activity recognition, Android development, evaluation, ubicomp research in the wild, and urban sensing. We also experimented with a new Visions of Ubicomp Film Contest. Last but not least, Jan Chipchase's keynote will offer a provocative look at the future of ubiquitous computing in new settings. We hope you find this year's program interesting, useful and enjoyable. Several organizations and people contributed to the success of UbiComp 2011 and we are grateful for their support. First, we would like to thank Tsinghua University for hosting and helping to organize UbiComp. We also appreciate the sponsorship of ACM SIGCHI, ACM SIGMOBILE and ACM SIGSPATIAL. Finally, the conference could not occur without the kind financial support of our benefactors Microsoft Research, Shanda, NSFC, NSF, Qualcomm, Google, IGRS, HTC, Nokia, Intel, AutoDesk, Opzoon, and Telezoon.