Without a ‘doubt’? Unsupervised discovery of downward-entailing operators.

Cristian Danescu-Niculescu-Mizil, Lillian Lee, and Richard Ducott.

Proceedings of NAACL HLT, pp. 137--145, 2009.


Teaser Answer:           


One can not answer this question without knowing whether hon is a “downward-entailing operator” or not. 

If it is, like doubt*, then “We doubt it snowed.” implies  “We doubt it snowed with big flakes.”.

If it is not, like know, then  “We know it snowed with big flakes.” implies “We know it snowed.”

For a language processing system, all words look like hon:  there is no easy way to determine whether a word is downward-entailing operator (and there are many such operators in English and other languages, the vast majority of them missing from the existing hand-constructed lists).  In this paper we propose the first algorithm that can automatically discover such operators.

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Talk Slides

System Output

Related Paper:                Don’t ‘have a clue’?



An important part of textual inference is making deductions involving monotonicity, that is, determining whether a given assertion entails restrictions or relaxations of that assertion. For instance, the statement `We *know* the epidemic spread quickly' does not entail `We know the epidemic spread quickly via fleas', but `We *doubt* the epidemic spread quickly' entails `We doubt the epidemic spread quickly via fleas'. Here, we present the first algorithm for the challenging lexical-semantics problem of learning linguistic constructions that, like `doubt', are downward entailing (DE). Our algorithm is unsupervised, resource-lean, and effective, accurately recovering many DE operators that are missing from the hand-constructed lists that textual-inference systems currently use.




  author={Cristian Danescu-Niculescu-Mizil and Lillian Lee and  Richard Ducott},

  title={Without a `doubt'?  {Unsupervised} discovery of downward-entailing


  booktitle={Proceedings of NAACL HLT},