Finding ALL Answers to OBDA Queries Using Referring Expressions.

We explore how referring expressions can be used to enhance how a conjunctive query is answered over description logic knowledge bases in a way that allows one to return not only answers explicitly named by constant symbols, but also anonymous individuals that are entailed to satisfy the query, and to provide syntactic means for referring to such individuals. In particular, for the logics \(\text {Horn-}\mathcal{ALC}\) and \(\mathcal{EL}^{\bot }\), we focus on reporting all entailed answers, on techniques necessary to finitely describe such sets of answers, and on extensions to more complex logics and settings.