Machine Learning and Rule-based Approaches to Assertion Classification

Table 8

F-Measure of StAC When Run on Challenge and CMC Corpora with Subsets of Features Best in Italics

Corpus	Feature		Positive	Negative	Uncertain	Alter-Ass'n.
Challenge	Lexical Context	±4 word window	0.97	0.90	0.58	0.49
		Section headings	0.90	0	0	0.82
		±4 word window + section headings	0.97	0.90	0.58	0.86
	Syntactic Context	±2 link window	0.94	0.70	0.49	0.47
		Verbs	0.90	0.21	0.05	0.38
		±2 link window + verbs	0.94	0.72	0.48	0.52
CMC	Lexical Context	±4 word window	0.98	0.95	0.89	0.42
		Section headings	0.85	0	0	0
		±4 word window + section headings	0.98	0.95	0.89	0.42
	Syntactic Context	±2 link window	0.92	0.61	0.73	0.13
		Verbs	0.88	0.21	0.53	0
		±2 link window + verbs	0.92	0.62	0.75	0.25

CMC = Computational Medicine Center.

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