Dirk Van Gucht

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Nested relations generalize ordinary flat relations by allowing tuple values to be either atomic or set valued. The nested algebra is a generalization of the flat relational algebra to manipulate nested relations. In this paper we study the expressive power of the nested algebra relative to its operation on flat relational databases. We show that the flat(More)
A general model for spatial databases is considered, which extends the relational model by allowing as tuple components not only atomic values but also geometrical figures. The model, which is inspired by the work of Kanellakis, Kuper and Revesz on constraint query languages, includes a calculus and an algebra which are equivalent. Given this framework, the(More)
The current database research trend 1s towards systems whrch can deal with advanced data apphcatrons that go beyond the standard “enterprise” or “office” database apphcatron This trend 1s reflected m the research on extension architectures [5,18,21] and obJect-oriented databases [2,3,12,21] Along wrth thus trend, the need for better and easier-to-use(More)
We extend Chandra and Harel s seminal work on computable queries for re lational databases to a setting in which also spatial data may be present using a constraint based data model Concretely we introduce both coordinate based and point based query languages that are complete in the sense that they can express precisely all computable queries that are(More)