Report on the Eighth International Workshop on Knowledge Representation Meets Databases ( KRDB ) , September 15 , 2001

The Eighth International Workshop on Knowledge Representation Meets Databases (KRDB) was held at the Ponti cia Universit a Urbaniana, in Rome, right after VLDB 2001. KRDB was initiated in 1994 to provide an opportunity for researchers and practitioners from the two areas to exchange ideas and results. This year's focus was on Modeling, Querying andManaging Semistructured Data. The one day program included ten research papers, one invited talk, and a panel. Eight of the accepted papers addressed various topics related to representation of information and reasoning in XML, one was on data integration and one on transaction processing. The invited talk, by Georg Gottlob, was on wrapper generation, also adopting XML to express the result of the wrapping process. Georg Gottlob opened the program with the invited talk Declarative Information Extraction, Web Crawling and Recursive Wrapping with Lixto. Lixto is a system and method for the visual and interactive generation of wrappers for Web pages under the supervision of a human developer, for automatically extracting information from Web pages using such wrappers, and for translating the extracted content into XML. The talk addressed some advanced features of Lixto, such as disjunctive pattern de nitions, specialization rules, and Lixto's capability of collecting and aggregating information from several linked Web pages. These features have been exploited in a demo developed in the commercial domain of a bookstore. The four papers in the rst group applied concepts and techniques from logic to XML. In Containment and integrity constraints for XPath fragments, A. Deutsch and V. Tannen consider a fragment of XPath expressions, with variable bindings, and study the expression containment problem. In addition, they further restrict these expressions by imposing constraints on the input XML document, such as key constraints, or referential integrity constraints. Depending on the XPath fragment (for expressions and constraints) the authors show the complexity of the containment problem to range from NP, to p