Consistent Query Answering for Expressive Constraints under Tuple-Deletion Semantics

TL;DR

This paper investigates the computational complexity of consistent query answering in relational databases with expressive constraints, identifying tractable subclasses and first-order rewritable cases under tuple-deletion semantics.

Contribution

It introduces a generalized class of schema constraints and analyzes the complexity of query answering and repair checking, discovering new tractable subclasses.

Findings

Identifies complexity boundaries for consistent query answering.

Defines new subclasses of constraints with tractable solutions.

Shows some problems are first-order rewritable.

Abstract

We study consistent query answering in relational databases. We consider an expressive class of schema constraints that generalizes both tuple-generating dependencies and equality-generating dependencies. We establish the complexity of consistent query answering and repair checking under tuple-deletion semantics for different fragments of the above constraint language. In particular, we identify new subclasses of constraints in which the above problems are tractable or even first-order rewritable.