On the complexity of data disjunctions

Abstract

We study the complexity of data disjunctions in disjunctive deductive databases (DDDBs). A data disjunction is a disjunctive ground clause $\text{R(}\text{c}\text{̄}{}_1\text{)⋯R(}\text{c}\text{̄}{}_{\mathrm{k}}\text{)}$, $\text{k⩾2}$, which is derived from the database such that all atoms in the clause involve the same predicate $\text{R}$. We consider the complexity of deciding existence and uniqueness of a minimal data disjunction, as well as actually computing one, both for propositional (data) and nonground (program) complexity of the database. Our results extend and complement previous results on the complexity of disjunctive databases, and provide newly developed tools for the analysis of the complexity of function computation.