Tense, Quantifiers, and Contexts

This paper describes a compositional semantics for temporal expressions as part of the meaning representation language (MRL) of the JANUS system, a natural language understanding and generation system under joint development by BBN Labs and ISI. The analysis is based on a higher-order intensional logic described in detail in Hinrichs (1987a). Temporal expressions of English are translated into this language as quantifiers over times that bind temporal indices on predicates. The semantic evaluation of time-dependent predicates is defined relative to a set of discourse contexts, which, following Reichenbach (1947), include the parameters of speech time and reference time. The resulting context-dependent and multi-indexed interpretation of temporal expressions solves a set of well-known problems that arise when traditional systems of tense logic are applied to natural language semantics. Based on the principle of rule-to-rule translation, the compositional nature of the analysis provides a straightforward and well-defined interface between the parsing component and the semantic-interpretation component of JANUS.