Foreword to Invited Articles Issue

These papers were recommended by the program chairs of the respective conferences as the best papers to be invited for submission, and they were accepted for publication after a full peer-review process according to TODS policies. The first four articles were selected from SIGMOD 2013. The article I/O-Efficient Algorithms on Triangle Listing and Counting by Xiaocheng Hu, Yufei Tao, and Chin-Wan Chung provides I/O and CPU efficient algorithms for counting and listing triangles in undirected graphs where a triangle is a clique involving three vertices. The proposals do not rely on assumptions made by previous approaches, and empirical studies show very good performance when compared to existing proposals. The article Discovering XSD Keys from XML Data Vansummeren studies the problem of discovering XML keys from XML data. In doing so, the article studies the problem of reasoning about XML keys, providing novel insight into aspects such as the testing for consistency, boundedness, satisfiability, universality, and equivalence. The article provides a mining algorithm that builds on these insights, and it includes an empirical study. a lock manager for database server hardware platforms that contain increasingly large numbers of cores. The lock manager, implemented in MySQL, offers reduced latching and features staged allocation and deallocation of locks so that allocation and deallocation can be performed in bulk. The article Lightweight Query Authentication on Streams by Stavros Papadopoulos, Graham Cormode, Antonios Deligiannakis, and Minos Garofalakis considers a setting where the processing of queries on a collection of streams is to be outsourced to an untrusted server. The article provides techniques that enable authentication of the results of important types of queries on streaming data. The techniques are lightweight and offer strong cryptographic guarantees. The next three articles are from PODS 2013. The article Na¨ıve Evaluation of Queries over Incomplete Databases by Amélie Gheerbrandt, Leonid Libkin, and Cristina Sirangelo provides a framework that makes it possible to identify classes of queries for which so-called na¨ıve evaluation yields certain answers. Further, the article applies the framework to different semantics of incompleteness, showing that many classes of queries exist for which na¨ıve evaluation is well suited, including, for example, positive first-order formulae for closed-world semantics. The article The Complexity of Mining Maximal Frequent Subgraphs by Benny Kimelfeld and Phokion G. Kolaitis considers an important graph-mining problem, that of finding maximal frequent subgraphs. Specifically, it provides a compressive study of the complexity of finding such subgraphs when …