Sound, Complete and Minimal UCQ-Rewriting for Existential Rules
This work addresses query rewriting in ontology-based data access, providing a foundational but incremental improvement for database and AI systems.
The paper tackles the problem of Ontology-Based Data Access by developing a sound, complete, and minimal rewriting technique for existential rules, focusing on a generic breadth-first algorithm and piece-unifiers, with experimental validation.
We address the issue of Ontology-Based Data Access, with ontologies represented in the framework of existential rules, also known as Datalog+/-. A well-known approach involves rewriting the query using ontological knowledge. We focus here on the basic rewriting technique which consists of rewriting the initial query into a union of conjunctive queries. First, we study a generic breadth-first rewriting algorithm, which takes as input any rewriting operator, and define properties of rewriting operators that ensure the correctness of the algorithm. Then, we focus on piece-unifiers, which provide a rewriting operator with the desired properties. Finally, we propose an implementation of this framework and report some experiments.