Bridging the Gap Between Scope-based and Event-based Negation/Speculation Annotations: A Bridge Not Too Far

摘要

We study two approaches to the marking of extra-propositional aspects of statements in text: the task-independent cue-and-scope representation considered in the CoNLL-2010 Shared Task, and the tagged-event representation applied in several recent event extraction tasks. Building on shared task resources and the analyses from state-of-the-art systems representing the two broad lines of research, we identify specific points of mismatch between the two perspectives and propose ways of addressing them. We demonstrate the feasibility of our approach by constructing a method that uses cue-and-scope analyses together with a small set of features motivated by data analysis to predict event negation and speculation. Evaluation on BioNLP Shared Task 2011 data indicates the method to outperform the negation/speculation components of state-of-the-art event extraction systems.