Proceedings of the twenty-eigth ACM SIGMOD-SIGACT-SIGART symposium on principles of database systems, PODS'09, Providence, Rhode Island, USA, June 29 - July 1, 2009

This volume contains the proceedings of the Twenty-eighth ACM SIGMOD-SIGACT-SIGART Symposium on Principles of Database Systems (PODS 2009), held in Providence, Rhode Island, on June 29--July 1, 2009, in conjunction with the 2009 ACM SIGMOD International Conference on Management of Data. The proceedings include 3 invited papers and 26 contributed papers. One invited paper is based on the keynote address by Raghu Ramakrishnan, while the other two are based on the invited tutorials by Leonid Libkin and Lars Arge, respectively. In addition, the announcement of the 2009 ACM PODS Alberto O. Mendelzon Test-of-Time Award also appears in the proceedings. The program committee selected 26 contributed papers for presentation at the conference from 97 submissions by authors from 21 countries. Most of the selected papers are preliminary reports on work in progress. While they have been read by the program committee members, they have not been formally refereed. It is expected that many of them will eventually appear in more polished and detailed form in scientific journals. In addition, the program committee also selected the paper "Size and Treewidth Bounds for Conjunctive Queries" by Georg Gottlob, Stephanie Lee, and Gregory Valiant for the PODS 2009 Best Paper Award, and the paper "XPath Evaluation in Linear Time with Polynomial Combined Complexity" by Pawel Parys for the PODS 2009 Best Student Paper Award, a new award for the PODS conferences. Warmest congratulations to the authors of these papers.