Paper: Jointly Combining Implicit Constraints Improves Temporal Ordering

ACL ID D08-1073
Title Jointly Combining Implicit Constraints Improves Temporal Ordering
Venue Conference on Empirical Methods in Natural Language Processing
Session Main Conference
Year 2008

Previous work on ordering events in text has typically focused on local pairwise decisions, ignoring globally inconsistent labels. How- ever, temporal ordering is the type of domain in which global constraints should be rela- tively easy to represent and reason over. This paper presents a framework that informs lo- cal decisions with two types of implicit global constraints: transitivity (A before B and B be- foreC implies AbeforeC) and time expression normalization (e.g. last month is before yes- terday). We show how these constraints can be used to create a more densely-connected network of events, and how global consis- tency can be enforced by incorporating these constraints into an integer linear programming framework. We present results on two event ordering tasks, showing a 3.6% abs...