Query Answering over Ontologies Using Controlled Natural Languages

In this thesis we define and study the expressive power and the data complexity of a certain number controlled languages for ontology-based data access systems (OBDASs), in which data stored in relational databases is queried through an ontology (i.e., a “conceptual” or “intensional”) middle layer and can be modeled by description logics. Controlled languages and controlled language interfaces have been proposed as a means of enhancing the usability of human interfaces to information systems, and, in particular to OBDASs. Controlled languages are subsets of natural languages (such as English) with a limited vocabulary and syntax, designed to avoid the ambiguity inherent to arbitrary natural language utterances, that is very difficult to process.