Table 12.

Technologies used in Task 1a from the participating systems along with the feature representation of the documents

Reference	Approach	Technologies	Features
[32]	flat	SVMs, MetaLabeler [44]	unigrams, bigrams
[37]	hierarchical	SVMs, Bayes networks	unigrams, bigrams
[45]	flat	MetaMap [46],	unigrams
		information retrieval,
		search engines
[48]	flat	k-NN, SVMs	unigrams, bigrams,
			trigrams
[49]	flat	k-NN, learning-to-rank	unigrams

Unigrams, bigrams and trigrams refer to the word level.