Equivalence of views by query capacity
The ability of view users to retrieve information contained in a database is studied. A measure of this ability, called ``query capacity'', is introduced and shown to be valuable for defining important concepts concerning views. Three such notions, namely equivalence, redundancy, and decomposition of views, are identified and investigated. A key tool, called ``template substitution'', is introduced to aid in these investigations. Among the major results obtained are the following: (1) Characterizations of view equivalence and redundancy in views. (2) The decidability of view equivalence. (3) A technique to eliminate redundancy in views. (4) The decomposition of a view into an essentially unique normal form.
scientific article; zbMATH DE number 4016238
scientific article