In the early days of database research, issues related to database semantics played a prominent role, and papers discussing database models, conceptual design, integrity constraints, normalization often dominated major database conferences. This began to change more than a decade ago, and nowadays those issues do not appear to be part of the mainstream database research. This situation is caused by several reasons: the problem began to be too difficult, the community was hoping on solutions based on better database models, the variety of buzzwords for new models and approaches required foundation and clarification, the problems raised by application required a lot of research, the pending hope on a universal, simple and genius solutions. Nevertheless the semantical foundations are left open for most of the modern database models or are not existing for models such as UML or XML. At the same time, the community was forgetting the achievements of the early database research.

The seminar "Semantics in databases" will be a forum for researchers still interested in database semantics and which can contribute on the basis of research on database semantics and modern approaches of logics, algebra and combinatorics to the solution of very difficult problems raised in application. The first workshop "Semantics in Databases" has been organized in Rez in January 1995. The results of the discussions of the workshop have been summarized in the post workshop proceedings published in LNCS 1358.

Semantics of databases and information systems can be based on approaches which have been developed and successfully used by different communities: the logics community especially those working on non-monotonic reasoning, theorem proving, deduction, abduction, induction, finite model theory, constraint problems, non-classical semantics and categorical foundations; the type theory community especially those working on algebraic foundations of information systems; the complexity theory community especially those working on combinatorial foundations of information systems complexity; the database theory community which has been continuing research on constraints; the AI community especially those working on agents, application of non-classical logics and reasoning, deduction, abduction, induction in data and knowledge bases and non-monotonic reasoning; the database community especially those contributing to foundations of information systems design including Web-based information systems, temporal aspects, integrity and security and database dynamics.

Research on semantics of databases is forced by a variety of problems challenging the modern information society. First, modern approaches are based on complex database and information system models. It requires the reformulation of classical results and their re-summarization including the restoration of older results. Dynamic semantics remains to be still open. Almost nothing is known on interaction semantics. Second, current technology faces difficult challenges. Information systems are becoming part of the everyday's infrastructure. They are used mainly by unexperienced users mainly on the basis of natural language understanding. The success of the internet caused the utilization of huge varieties of semantics. XML and other ML are becoming the baseplate of internet applications. However, XML supports semantics and consistency to a very limited extend. Third, the importance of research on semantics is hyper-raising by applications. Applications are more and more decentralized and require careful integration. UML become to be the 'inter-galactic' application specification language. It has almost no semantics. In order to develop consistent application the semantics foundation needs to be worked out.

This Dagstuhl seminar aims in bringing together different communities such as the database theory community, the logics community, the AI community, the complexity theory community, the type theory community and the database applications community. The aim of the seminar is to provide a working environment where: different streams of semantics research are becoming aware of research of other communities; maintaining the database semantics community; working on plans for a survey on semantics in databases; discussing challenges of modern applications to semantics; figuring out research challenges of the next decade. To encourage discussion, we will have talks with a responder. The length of a talk is restricted to 60 minutes. The talk is followed by a discussion introduced by the responder of about 30 minutes overall.