Accession Number:

ADA135105

Title:

On Acyclic Database Decompositions.

Descriptive Note:

Technical rept.,

Corporate Author:

STANFORD UNIV CA DEPT OF COMPUTER SCIENCE

Personal Author(s):

Report Date:

1983-07-01

Pagination or Media Count:

13.0

Abstract:

Given a universal relation scheme, presented as a set of attributes and a set of dependencies, it may be advantageous ot decompose it into a collection of schemes, each with its own sets of attributes and dependencies, which has some desired properties. A basic requirement for such a decomposition to be useful is that the corresponding decomposition map on universal relations be injective. A central problem in database theory is to find the reconstruction map, i.e., the inverse map of an injective decomposition map. We prove here that when the decomposition, viewed as a hypergraph, is acrylic and the given dependencies are full implicational dependencies, then the reconstruction map is the natural join. Based on this, we show that there is a polynomial time algorithm to test for injectiveness of decompositions.

Subject Categories:

  • Theoretical Mathematics

Distribution Statement:

APPROVED FOR PUBLIC RELEASE