Hypothetical Temporal Queries in Databases

This paper considers the problem of posing and answering hypothetical temporal queries to databases. The queries are hypothetical in the sense that we pose a query to a virtually updated database, and the query is answered on the basis of the initial, physical database and the list of transactions that virtually update the database. The queries are temporal in the sense that they refer to possibly all the states along which the database evolves from the initial database and the nal virtual state. The possibility of answering such queries relies on a speciication of the dynamics of the database augmented with a spec-iication of the dynamics of auxiliary tables that have their origin in the temporal subfor-mulas of the query and encode the history of the database. Queries are posed in rst order past temporal logic. These functionalities are implemented in SCDBR, an automated rea-soner for speciications of database updates. Although we concentrate mostly on relational databases, the methodology can be applied to other kinds of databases, as deductive and rst order databases. The copyright of this paper belongs to the paper's authors. Permission to copy without fee all or part of this material is granted provided that the copies are not made or distributed for direct commercial advantage.