Automatic Time Expression Labeling for English and Chinese Text

In this paper, we describe systems for automatic labeling of time expressions occurring in English and Chinese text as specified in the ACE Temporal Expression Recognition and Normalization (TERN) task. We cast the chunking of text into time expressions as a tagging problem using a bracketed representation at token level, which takes into account embedded constructs. We adopted a left-to-right, token-by-token, discriminative, deterministic classification scheme to determine the tags for each token. A number of features are created from a predefined context centered at each token and augmented with decisions from a rule-based time expression tagger and/or a statistical time expression tagger trained on different type of text data, assuming they provide complementary information. We trained one-versus-all multi-class classifiers using support vector machines. We participated in the TERN 2004 recognition task and achieved competitive results.