The third PASCAL Recognizing Textual Entailment Challenge (RTE-3) contained an optional task that extended the main entailment task by requiring a system to make three-way entailment decisions (entails, contradicts, neither) and to justify its response. Contradiction was rare in the RTE-3 test set, occurring in only about 10% of the cases, and systems found accurately detecting it difficult. Subsequent analysis of the results shows a test set must contain many more entailment pairs for the three-way decision task than the traditional two-way task to have equal confidence in system comparisons. .
