From Causes for Database Queries to Repairs and Model-Based Diagnosis and Back

TL;DR

This paper explores the connections between causes for database query answers, database repairs, and diagnosis, providing new insights and algorithms for causality and repair computation by linking these areas.

Contribution

It establishes formal links between causality, repairs, and diagnosis in databases, enabling the transfer of techniques and results across these fields.

Findings

Database repairs can be derived from causes for query answers.

Diagnosis methods can identify causes and responsibilities in databases.

New algorithms and complexity results for causality problems were developed.

Abstract

In this work we establish and investigate connections between causes for query answers in databases, database repairs wrt. denial constraints, and consistency-based diagnosis. The first two are relatively new research areas in databases, and the third one is an established subject in knowledge representation. We show how to obtain database repairs from causes, and the other way around. Causality problems are formulated as diagnosis problems, and the diagnoses provide causes and their responsibilities. The vast body of research on database repairs can be applied to the newer problems of computing actual causes for query answers and their responsibilities. These connections, which are interesting per se, allow us, after a transition -inspired by consistency-based diagnosis- to computational problems on hitting sets and vertex covers in hypergraphs, to obtain several new algorithmic and complexity results for database causality.