On the expressive power of the relational algebra with partially ordered domains

Ng, W. and Levene, Mark and Fenner, Trevor (2000) On the expressive power of the relational algebra with partially ordered domains. International Journal of Computer Mathematics 74 (1), pp. 53-62. ISSN 0020-7160.

Full text not available from this repository.

Official URL: https://doi.org/10.1080/00207160008804922

Abstract

Assuming data domains are partially ordered, we define the partially ordered relational algebra (PORA) by allowing the ordering predicate ⊑ to be used in formulae of the selection operator σ. We apply Paredaens and Bancilhon's Theorem to examine the expressiveness of the PORA, and show that the PORA expresses exactly the set of all possible relations which are invariant under order-preserving automorphisms of databases. The extension is consistent with the two important extreme cases of unordered and linearly ordered domains. We also investigate the three hierarchies of: (1) computable queries, (2) query languages and (3) partially ordered domains, and show that there is a one-to-one correspondence between them.

Metadata

Item Type:	Article
School:	Birkbeck Faculties and Schools > Faculty of Science > School of Computing and Mathematical Sciences
Depositing User:	Sarah Hall
Date Deposited:	16 Mar 2021 20:25
Last Modified:	09 Aug 2023 12:50
URI:	https://eprints.bbk.ac.uk/id/eprint/43541

Statistics

Archive Staff Only (login required)

Edit/View Item