In ontology-based data access, multiple data sources are integrated using anontology and mappings . The expressibility problem asks whether a givensource query $q_s$ is expressible as a target query . We consider (U)CQsas source and target queries and GAV mappings, showing that both problems are $Pi^p_2$-complete in DL-Lite, coNExpTime-complete between EL and ELHI whensource queries are rooted . The verification problem asks, additionally given acandidate target query $Q_t$, whether $q_.t$ expresses $q#s$

Author(s) : Carsten Lutz, Johannes Marti, Leif Sabellek

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Keywords : query - q - data - target - asks -

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