Proceedings of the 4th ACM international workshop on Hot topics in planet-scale measurement, HotPlanet@MobiSys 2012, Ambleside, United Kingdom, June 25-29, 2012

It is our great pleasure to welcome you to the 4th ACM International Workshop on Hot Topics in Planet-Scale Measurement -- HotPlanet'12. This year's workshop is motivated by the fact that successfully researching, designing and building new mobile, ad-hoc, mesh, and opportunistic networking systems and algorithms requires access to large-scale data on human mobility, encounter, and social network patterns. Unfortunately, the wireless and mobile research communities lack such large-scale data. We believe that large-scale datasets are important, not only in communication network design, but also for fundamental study in other academic disciplines, e.g., epidemiology, urban planning, and social science. Complex networks research has flourished since 1989 when the first large Internet (and later WWW) datasets became available. To achieve similar improvements in mobile networking and related fields, large-scale, and ideally planet-scale, datasets must be collected and made available. Following three previous successful editions of the workshop at ACM MobiSys 2009, 2010, and 2011, the fourth HotPlanet workshop will challenge the community to collect large-scale human mobility traces as well as to propose novel mobility data processing and knowledge discovery techniques. The program committee accepted 7 papers that cover a variety of topics including emerging applications involving large-scale human mobility data collection, human dynamics characterization and modelling, knowledge discovery from mobility data, and methods for choosing and collecting large-scale human mobility datasets. In addition, the program includes a keynote speech on Through a Graph, Darkly by Jon Crowcroft, who has a lot of experience in collecting human mobility datasets and investigating social network patterns. We hope that these proceedings will serve as a valuable reference for large-scale wireless networking measurement.