ACM, 2012. This is the authors version of the work. It is posted here by permission of ACM for your personal use. Not for redistribution. The definitive version was published in Proceedings of the 8th ACM International Workshop on the Foundations of Mobile Computing (FOMC'12). ACM, New York, NY, USA.
Joanne Talbot Hanley
Last modified: Mon Aug 6 16:18:39 EDT 2012