  Most existing natural language database interfaces (NLDBs) were designed to
be used with database systems that provide very limited facilities for
manipulating time-dependent data, and they do not support adequately temporal
linguistic mechanisms (verb tenses, temporal adverbials, temporal subordinate
clauses, etc.). The database community is becoming increasingly interested in
temporal database systems, that are intended to store and manipulate in a
principled manner information not only about the present, but also about the
past and future. When interfacing to temporal databases, supporting temporal
linguistic mechanisms becomes crucial.
  We present a framework for constructing natural language interfaces for
temporal databases (NLTDBs), that draws on research in tense and aspect
theories, temporal logics, and temporal databases. The framework consists of a
temporal intermediate representation language, called TOP, an HPSG grammar that
maps a wide range of questions involving temporal mechanisms to appropriate TOP
expressions, and a provably correct method for translating from TOP to TSQL2,
TSQL2 being a recently proposed temporal extension of the SQL database
language. This framework was employed to implement a prototype NLTDB using ALE
and Prolog.
