From structure to interpretation : A double-layered annotation for event factuality

Current work from different areas in the field points out the need for systems to be sensitive to the factuality nature of events mentioned in text; that is, to recognize whether events are presented as corresponding to real situations in the world, situations that have not happened, or situations of uncertain status. Event factuality is a necessary component for representing events in discourse, but for annotation purposes it poses a representational challenge because it is expressed through the interaction of a varied set of structural markers. Part of these factuality markers is already encoded in some of the existing corpora but always in a partial way; that is, missing an underlying model that is capable of representing the factuality value resulting from their interaction. In this paper, we present FactBank, a corpus of events annotated with factuality information which has been built on top of TimeBank. Together, TimeBank and FactBank offer a double-layered annotation of event factuality: where TimeBank encodes most of the basic structural elements expressing factuality information, FactBank adds a representation of the resulting factuality interpretation.

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