Controlled English for DL-Lite

As it is well-known, querying and managing structured data in natural language is a challenging task due to its ambiguity (syntactic and semantic) and its expressiveness. On the other hand, querying, for example, a database is a well-defined and unambigous task, namely, that of evaluating some formal query (e.g. an SQL query) of a limited expressiveness over some finite structure: the instance of the database schema. However these formal query languages may be utterly obscure for the casual user. To bridge this gap, the use of controlled languages has been proposed. Controlled languages are fragments of, say, English, with a limited vocabulary and a very restricted set of grammar rules, but in which ambiguity is minimal if not alltogether unexistent. Moreover, they can be engineered in a way that a meaning representation built out from some logic can be compositionally constructed during parsing. A logic ideally matching the expressive powerof a formal query language being able to be taken as such. As a first step to building such a language we study the crucial issue of the expressive power of the logic to which it should translate in the back end: DL-Lite, that we believe well-adapted for querying and specifying data. To this end, we inspect a certain number of tractable fragments of English that compostionally translate into fragments of first order logic (FOL), tractable in that the satisfiability problem (SAT) for these induced fragments of FOL is in P, and compare them to DL-Lite w.r.t. expressive power.