Independence of logic database queries and update

摘要

A query is independent of an update if executing the update cannot change the result of evaluating the query. The theorems of this paper give methods for proving independence in concrete cases, taking into account integrity constraints, recursive rules, and arbitrary queries. First we define the notion of independence model-theoretically, and we prove basic properties of the concept. Then we provide proof-theoretic conditions for a conjunctive query to be independent of an update. Finally, we prove correct an induction scheme for showing that a recursive query is independent of an update.