Lenzerini

Inspired by recent work on higher-order Description Logics, we propose HOS, a new semantics for OWL 2 QL ontologies. We then consider SPARQL queries which are legal under the direct semantics entailment regime,we extend them with logical union, existential variables, and unrestricted use of variables so as to express meaningful meta-level queries. We show that both satisfiability checking and answering instance queries with metavariables have the same ABox complexity as under direct semantics.