In late May, 2008, a group of database researchers, architects, users and pundits met at the Claremont Resort in Berkeley, California to discuss the state of the research field and its impacts on practice. This was the seventh meeting of this sort in twenty years, and was distinguished by a broad consensus that we are at a turning point in the history of the field, due both to an explosion of data and usage scenarios, and to major shifts in computing hardware and platforms. Given these forces, we are at a time of opportunity for research impact, with an unusually large potential for influential results across computing, the sciences and society. This report details that discussion, and highlights the group's consensus view of new focus areas, including new database engine architectures, declarative programming languages, the interplay of structured and unstructured data, cloud data services, and mobile and virtual worlds. We also report on discussions of the community's growth, including suggestions for changes in community processes to move the research agenda forward, and to enhance impact on a broader audience.

Database research is expanding, with major efforts in system architecture, new languages, cloud services, mobile and virtual worlds, and interplay between structure and text.

726 participants. The conference received a record number of submissions as compared to previous years of VLDB.• The Research Track received 659 submissions, of which 134 papers (20 %) were accepted. Out of 134 accepted papers, 78 were accepted in the first round, and 56 were accepted after they were resubmitted with revisions and a second round of reviewing. In addition, VLDB 2012 also included three keynote talks, pre-and post-conference workshops, tutorials, and panels. The journal versions of seven best papers that appeared in the conference are included in this special issue of the VLDB Journal. These invited papers are substantially improved, revised, and extended as compared to their original conference versions and were accepted for publication after several rounds of journal-style reviewing. These papers cover a wide range of current database research topics, namely realtime graph data management, graph querying and indexing, social tagging of web data, probabilistic data consistency, adaptive indexing for transactional workloads, incremental view maintenance under high-rate updates, and storage provisioning.The first paper of this special issue "Dense Subgraph Maintenance under Streaming Edge Weight Updates for Real-time Story Identification" (by Albert Angel, Nick Koudas, Nikos Sarkas, Divesh Srivastava, Michael Svendsen, and Srikanta Tirthapura) is also selected for the best paper award for VLDB 2012 conference. This paper addresses the problem of real-time story identification using social media data, such as daily blog posts and status updates, posted by millions of people around the globe. The main challenge the authors address is the efficient maintenance of dense subgraphs corresponding to groups of tightly coupled entities, under streaming updates of edge weights. Based on novel theoretical results on the amount of change resulting from a single edge weight update, authors present an algorithm for dense subgraph maintenance and demonstrate its performance with a thorough experimental evaluation.

We present SSS, a scalable transactional key-value store deploying a novel distributed concurrency control that provides external consistency for all transactions, never aborts read-only transactions due to concurrency, all without specialized hardware. SSS ensures the above properties without any centralized source of synchronization. SSS's concurrency control uses a combination of vector clocks and a new technique, called snapshot-queuing, to establish a single transaction serialization order that matches the order of transaction completion observed by clients. We compare SSS against high performance key-value stores, Walter, ROCOCO, and a two-phase commit baseline. SSS outperforms 2PC-baseline by as much as 7x using 20 nodes; and ROCOCO by as much as 2.2x with long read-only transactions using 15 nodes.

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