Scheme Evolution and the Relationship Algebra. Revision
Abstract
This paper discusses extensions to the conventional relational algebra to support both aspects of transaction time, evolution of a database's contents and evolution of a database's scheme. The authors define a relation's scheme to be the relation's temporal signature, a function mapping the relation's attribute names onto their value domains, and class, indicating the extent of support for time. They also introduce commands to change a relation, now defined as a triple consisting of a sequence of classes, a sequence of signatures, and a sequence of states. A semantic type system is required to identify semantically incorrect expressions and to enforce consistency constraints among a relation's class, signature, and state following update. It is shown that these extensions are applicable, without change, to historical algebras that support valid time, yielding an algebraic programming language for the query and update of temporal databases. The additions preserve the useful properties of the conventional algebra. Keywords: Semantis, Syntax.
Document Details
- Document Type
- Technical Report
- Publication Date
- May 31, 1988
- Accession Number
- ADA201297
Entities
People
- Edwin Mckenzie
- Richard Snodgrass
Organizations
- University of North Carolina at Chapel Hill