Two string-based finite-state models of the semantics of calendar expressions

Abstract

This paper presents two string-based finite-state approaches to modelling the semantics of natural-language calendar expressions: extended regular expressions (XREs) over a timeline string of unique symbols, and a string of hierarchical periods of time constructed by finite-state transducers (FSTs). The approaches cover expressions ranging from plain dates and times of the day to more complex ones, such as the second Tuesday following Easter. The paper outlines the representations of sample calendar expressions in the two models, presents a possible application in temporal reasoning, and informally compares the models. © Springer-Verlag Berlin Heidelberg 2006.