A Compositional Semantics for a Wide-Coverage Natural-Language Query Interface to a Semantic Web Triplestore

Many Natural Language (NL) Query Interfaces to data stores convert queries to a formal query language and then execute the formal query in order to obtain the result. This is problematic when handling chained prepositional phrases. An alternative approach is to treat the NL query language as a formal language and to execute the NL query directly with respect to the data store. This approach can accommodate a wide range of NL queries and is relatively easy to implement if it is based on an extension of Richard Montague's denotational semantics (MS) for natural language. The higher-order functional capability of the programming language Haskell facilitates both the implementation of MS and the close integration of syntactic analysis with semantic processing. A publicly accessible web-based NL interface to a remote Semantic Web data store has been constructed to demonstrate the viability of this approach. The approach can be directly adapted for use with relational databases.

I. Introduction

Many Natural Language Query Interfaces to relational databases and semantic web triplestores convert the NL query to a formal query language such as SQL or SPARQL and then execute the formal query with respect to the relational database or semantic web triplestore respectively. One problem with these approaches is that the interface is restricted by the difficulty of translating complex NL phrases to the formal query language. In particular, queries with chained prepositional phrases containing quantifiers have been difficult to accommodate. Examples of such queries are: “who discovered two moons with a telescope in 1877 at us_naval_observatory,” and “where was a telescope used by hall to discover phobos”.