Uniqueness of Update Strategies for Database Views

Abstract

The problem of supporting updates to views of a database schema has been the focus of a substantial amount of research over the years. Since the mapping from base schema to view schema is seldom injective, there is usually a choice of possibilities for the reflection of view updates to base-schema updates. This work presents a solution to this problem which augments the constant-complement strategy of Bancilhon and Spyratos with order-theoretic properties to guarantee unique reflection of view updates. Specifically, most database formalisms endow the database states with a natural order structure, under which update by insertion is an increasing operation, and update by deletion is decreasing. Upon augmenting the original constant-complement strategy with compatible order-based notions, the reflection to the base schema of any update to the view schema which is an insertion, a deletion, or a modification which is realizable as a sequence of insertions and deletions is shown to be unique and independent of the choice of complement.