A model for temporal references and its application in a question answering program

摘要

A formal model is presented which represents the structure underlying temporal references in natural language. Serving as a framework for analysis of tenses, time relation, and other references to time in language, the model consists of a partially ordered set, called “time” and successively defined concepts such as “time-segment”, “duration”, “time-segment relation”, “tense”, “reference time”, and “tense marker”. This model is justified by making informal arguments, by giving English language examples, and by showing that it is a generalization of several other systems. A computer question answering program, “Chronos”, which uses the concepts of tense and time-segment relations, illustrates and supports the validity of the model. Chronos is shown to be a simple program which nevertheless can understand most of the temporal meaning in a sentence.