A Model for Temporal References and Its Application in a Question Answering Program

A formal model is pr.:sented which represents the .~'tructure underlying temporal references" in natural language. Sei'ting as a framework for analysis o f tenses, time relations, and other references to time i~: language, the model consists o f a partially ordered set, called "'time" and successively def,:ned concepts such as "'tinw.segment", "duration "'~, "'time.segment relation", "'tense", "'l eference time", and "'tense marker". This model is justified by making informal arguments, b ~ giving English language exr.mples, and by showing that it is a generalization of several other s):s.rems. A computer question answering pro/ram, "'Chronos", which use~ the concepts o f tense ,~lnd time-segment relations, illu.~.trates and supports the validity o f the model. Chronos is" sho~'n to be a simple program which nevertheless can understand most o f the temporal meaning ':[n a sentence.