Picking reference events from tense trees: a formal, implementable theory of English tense-aspect semantics

Despite numerous investigations into English tense-aspect semantics, the problem of formally interpreting tense and aspect remains in large part unsolved. A formal solution requires (a) a well-defined mapping from a subset of English covering the most common tense-aspect constructions (including embedded tensed clauses) to a formal meaning representation, and (b) a well-defined denotational semantics for the meaning representation, which accords with speakers' intuitions about the original text. We propose a simple structure called a tense tree (or a set of connected tense trees) as a basis for interpreting tense-aspect constructions and some time adverbials in a context-dependent way. The de-indexicalization process simultaneously transforms tense trees and logical forms, the former in accord with simple recursion equations and the latter in accord with formal equivalences between context-indexed and context-independent logical forms. The rules have been implemented, and yield meaning representations in a formal episodic logic for narrative understanding.