Improving event prediction by representing script participants
Summary
The paper addresses the automatic acquisition of script knowledge, i.e., knowledge about the typical course of events in everyday situations such as visiting a restaurant. Earlier unsupervised models were built on coreference chains and barely outperformed the simplest frequency baseline. Their weak point is entities that occur only once in a text: all of them fall into one shared category, so information about them is lost. The authors propose representing each event as a verb with labels for the scenario participants (participant-labeled events, PLE) in the subject, direct object and indirect object positions. Arguments are extracted with Stanford CoreNLP. Participant labels are assigned by the heuristic of Kampmann et al. (2015), which relies on WordNet hypernyms. The next event is predicted by a bigram model that counts event pairs with any number of intervening events (skip-all). The model was evaluated on the narrative cloze task on the Dinners from Hell and InScript corpora. It substantially outperforms the approaches of Pichotta & Mooney and Jans et al., as well as the frequency baseline, especially when the correct event has to be ranked near the top. Participant knowledge thus makes it possible to generalize from specific words to their roles in the scenario. The approach also combines crowdsourced script acquisition with unsupervised acquisition.
Key points
- On Dinners from Hell, the model reaches Recall@10 = 0.41. For comparison, P&M scores 0.26, Jans 0.25 and MostFreq 0.27. Its coverage is lower (0.757 vs. 0.809–0.957) because it makes no prediction for an unseen context.
- When predicting the full PLE, Recall@10 is 0.18 vs. 0.13. The authors present this result as a baseline for future work.
- Data: Dinners from Hell contains 143 blog stories about restaurant visits, 10 of which form the dev set. InScript has 910 stories collected via Mechanical Turk across 10 scenarios, about 90 per scenario. Testing uses document-level leave-one-out.
- Replacing automatic coreference chains with gold ones barely changes the result. Gold participant annotation, by contrast, gives a noticeable gain. The current automatic tagger reaches only 0.59 micro F.
- Across all 10 InScript scenarios, the model consistently outperforms previous approaches on Recall@1 and Recall@10.
Cite
@inproceedings{ahrendt2016improving,
title = {{Improving event prediction by representing script participants}},
author = {Ahrendt, Simon and Demberg, Vera},
booktitle = {Proceedings of the 2016 Conference of the North American Chapter of the Association for Computational Linguistics: Human Language Technologies},
year = {2016},
doi = {10.18653/v1/n16-1067},
url = {https://doi.org/10.18653/v1/n16-1067}
}References
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