Querying Structured Knowledge Sources

We present an implemented approach for domainrestricted question answering from structured knowledge sources, based on robust semantic analysis in a hybrid NLP system architecture. We build on a lexicalsemantic conceptual structure for question interpretation, which is interfaced with domain-specific concepts and properties in a structured knowledge base. Question interpretation involves a limited amount of domain-specific inferences and accounts for quantificational questions. We extract so-called proto queries from the linguistic representation, which provide partial constraints for answer extraction from the underlying knowledge sources. The search queries we construct from proto queries effectively constitute minimum spanning trees that restrict the possible answer candidates. Our approach naturally extends to multilingual question answering and has been developed as a prototype system for two application domains: the domain of Nobel prize winners and the domain of Language Technology, on the basis of the large ontology underlying the information portal LT World.