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Are You Sure that This Happened? Assessing the Factuality Degree of Events in Text| old_uid | 11148 |
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| title | Are You Sure that This Happened? Assessing the Factuality Degree of Events in Text |
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| start_date | 2012/03/23 |
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| schedule | 11h-12h30 |
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| online | no |
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| summary | Identifying the veracity, or factuality, of event mentions in text is fundamental for reasoning about eventualities in discourse. Inferences derived from events judged as not having happened, or as being only possible, are different from those derived from events evaluated as factual.
Event factuality involves two separate levels of information. On the one hand, it deals with polarity, which distinguishes between positive and negative instantiations of events. On the other, it has to do with degrees of certainty (e.g., possible, probable), an information level generally subsumed under the category of epistemic modality, and which has been widely discussed in linguistics and philosophy. In languages like English, these two levels of information are expressed through a variety of linguistic devices, from modal auxiliaries and polarity particles to syntactic constructions of different kind, passing through a number of lexical predicates, such as verbs and nouns conveying epistemic evaluations (e.g., believe, know, suspicion, idea).
This talk aims at contributing to a better understanding of how event factuality is articulated in natural language, with special focus on English data. For that purpose, I will present a linguistic-oriented computational model which has at its core an algorithm articulating the effect of factuality relations across levels of syntactic embedding. As a proof of concept, this model has been implemented in De Facto, a factuality profiler for eventualities mentioned in text, and tested against a corpus built specifically for the task, yielding an F-1 measure of 0.70 (macro-averaging) and 0.80 (micro-averaging). These two measures mutually compensate for an over-emphasis present in the other (either on the lesser or greater populated categories), and can therefore be interpreted as the lower and upper bounds of the De Facto's performance. |
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| responsibles | Candito |
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