On the Succinctness of Query Rewriting over OWL 2 QL Ontologies with Shallow Chases
Abstract
We investigate the size of first-order rewritings of conjunctive queries over OWL 2 QL ontologies of depth 1 and 2 by means of hypergraph programs computing Boolean functions. Both positive and negative results are obtained. Conjunctive queries over ontologies of depth 1 have polynomial-size nonrecursive datalog rewritings; tree-shaped queries have polynomial positive existential rewritings; however, in the worst case, positive existential rewritings can only be of superpolynomial size. Positive existential and nonrecursive datalog rewritings of queries over ontologies of depth 2 suffer an exponential blowup in the worst case, while first-order rewritings are superpolynomial unless . We also analyse rewritings of tree-shaped queries over arbitrary ontologies and observe that the query entailment problem for such queries is fixed-parameter tractable.
Cite
@article{arxiv.1401.4420,
title = {On the Succinctness of Query Rewriting over OWL 2 QL Ontologies with Shallow Chases},
author = {Stanislav Kikot and Roman Kontchakov and Vladimir Podolskii and Michael Zakharyaschev},
journal= {arXiv preprint arXiv:1401.4420},
year = {2014}
}