We focus on ontology-mediated queries (OMQs) based on (frontier-)guarded existential rules and (unions of) conjunctive queries . We investigate theproblem of FO-rewritability, i.e., whether an OMQ can be rewritten as afirst-order query . We adopt two different approaches to solving the problem: the first approachemploys standard two-way alternating parity tree automata . The second approach relies on a sophisticated automatamodel, known as cost automata. This allows us to show that our problem is2ExpTime-complete .

Author(s) : Pablo Barcelo, Gerald Berger, Carsten Lutz, Andreas Pieris

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Keywords : queries - order - automata - ontology - mediated -

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