Learning to recognize features of valid textual entailments

This paper advocates a new architecture for textual inference in which finding a good alignment is separated from evaluating entailment. Current approaches to semantic inference in question answering and textual entailment have approximated the entailment problem as that of computing the best alignment of the hypothesis to the text, using a locally decomposable matching score. We argue that there are significant weaknesses in this approach, including flawed assumptions of monotonicity and locality. Instead we propose a pipelined approach where alignment is followed by a classification step, in which we extract features representing high-level characteristics of the entailment problem, and pass the resulting feature vector to a statistical classifier trained on development data. We report results on data from the 2005 Pascal RTE Challenge which surpass previously reported results for alignment-based systems. translator kidnapped in Iraq no 98 Sharon warns Arafat could be targeted for assassination. prime minister targeted for assassination no 152 Twenty-five of the dead were members of the law enforcement agencies and the rest of the 67 were civilians. 25 of the dead were civilians. no 231 The memorandum noted the United Nations estimated that 2.5 million to 3.5 million people died of AIDS last year. Over 2 million people died of AIDS last year. yes 971 Mitsubishi Motors Corp.'s new vehicle sales in the US fell 46 percent in June. Mitsubishi sales rose 46 percent. no 1806 Vanunu, 49, was abducted by Israeli agents and convicted of treason in 1986 after discussing his work as a mid-level Dimona technician with Britain's Sunday Times newspaper. Vanunu's disclosures in 1968 led experts to conclude that Israel has a stockpile of nuclear warheads. no 2081 The main race track in Qatar is located in Shahaniya, on the Dukhan Road. Qatar is located in Shahaniya. no Table 1: Illustrative examples from the PASCAL RTE data set, available at http://www.pascal-network.org/Challenges/RTE. Though most problems shown have answer no, the data set is actually balanced between yes and no.