Presents a critical review of linguistic research on the temporal structure of sentences, with particular reference to the progressive aspect of the English verb. All works reviewed analyze the temporal meaning of these forms using the concepts of "Interval Semantics" and the methods of logical analysis. (MES)

Outlines a system that modifies, and expands on, PTQ ("The Proper Treatment of Quantification in English" by R. Montague), in order to include an analysis of the present and past tenses, and of the perfect and progressive aspects. Also analyzes temporal adverbs and their interactions with tense and aspect. (MES)

Expanded version of an article originally written under the auspices of the 1970 MSSB Advanced Research Seminar in Mathematical Linguistics and presented at the Annual Meeting of the Association for Computational Linguistics, July 23, 1970, Columbus, Ohio. (DD)