Expressing DL-Lite ontologies with Controlled English
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In this paper we deal with the problem of providing natural language front-ends to databases upon which an ontology layer has been added. Specifically, we are interested in expressing ontologies formalized in Description Logics in a controlled language, i.e., a fragment of natural language tailored to compositionally translate into a knowledge representation (KR) language. As KR language we have chosen DL-LiteR , a representative of the well-known DL-Lite family, and we aim at understanding the kind of English constructs the controlled language can and cannot have to correspond to DL-LiteR . Hence, we compare the expressive power of DL-LiteR to that of various fragments of English studied by I. Pratt and A. Third, which compositionally translate into fragments of first order logic. Our analysis shows that DL-LiteR , though itself tractable, is incomparable in expressive power with respect to tractable fragments of English. Interestingly, it allows one to represent a restricted form of relative clauses, which lead to intractability when used without restrictions on the occurrences of negations, and existential quantifiers.