Acknowledgements

Many thanks to Fahiem Bacchus, Rajeev Goré, Marco Pistore, Ron van der Meyden, Moshe Vardi, and Lenore Zuck for useful discussions and comments, as well as to the anonymous reviewers and to David Smith for their thorough reading of the paper and their excellent suggestions. Sylvie Thiébaux, Charles Gretton, John Slaney, and David Price thank National ICT Australia for its support. NICTA is funded through the Australian Government's Backing Australia's Ability initiative, in part through the Australian Research Council. Froduald Kabanza is supported by the Canadian Natural Sciences and Engineering Research Council (NSERC).