Temporal databases incorporate the concept of time to create high-level abstractions useful in database applications. This has been an active area of research for about twenty years. In the last few years the importance of the temporal database area has been recognized by the international scientific community. This recognition came in part in the form of the ARPA/NSF sponsored International Workshop on Temporal Database Infrastructure in 1993, a VLDB-affiliated temporal workshop in 1995, a special section of the IEEE Transactions on Knowledge and Data Engineering on temporal and real time databases published in August 1995, and the incorporation of temporal constructs, proposed by the temporal database community, in the soon-to-be standardized SQL3 language.

This report arose out of the Dagstuhl seminar that was organized by us during June 23–27, 1997. This seminar focused on the future directions of this discipline, with respect to both research issues and the means to incorporate temporal databases into main-stream application development. List of topics discussed at this seminar included:

1. Temporal data models: relational, object-oriented, deductive and hybrid models. Where do the temporal capabilities fit in?
2. Temporal languages: TSQL2 and beyond. Update and retrieval languages for various types of temporal data models.
3. 3The inter-relationships between temporal databases and other disciplines: spatial databases, active databases, deductive databases, realtime databases, information uncertainty, belief revision, etc.
4. Implementation issues in temporal databases. Issues that arise from experience of implementors and users and the agenda for research into these areas and transition to use in practice.
5. Strategic discussions about the future of “temporal databases” as a discipline. Evaluation of the current state of the art and “call for action” to the community.

The Dagstuhl seminar brought together researchers that have dealt with different perspectives of temporal databases: temporal data models, temporal retrieval and update languages, inter-relationships between temporal databases and other database technologies (e.g., spatial databases, active databases, real-time databases), and inter-relationships between temporal databases and temporal reasoning in artificial intelligence. Some of the invited participants have also been involved in the standardization activities of the temporal community. Having a diverse group that shared a focus on temporal information processing ensured critical evaluation of the activities that have occurred thus far, and enriched the discussions.

As any Dagstuhl seminar, the participants respresented a select group of prominent researchers in the subject area. We also solicited submission for a book, aimed to include high-quality original papers about the state-of-theart in the temporal database area. The book entitled “Temporal databases - research and practice” will be published by Springer-Verlag.

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