Expressing DL-lite ontologies with controlled English

We are interested in providing natural language front-ends to databases upon which an ontology layer has been added. Specifically, here we deal with how to express 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 [3, 4], 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 FOL identified by Pratt and Third as corresponding to fragments of English [8]. 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.