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 Question:           


Does the statement “We hon it snowed with big flakes.” imply  “We hon it snowed.”?

Or is it the other way around? 

The point is to try answering this question without knowing what the verb hon means. (If you are a Star Trek fanatic you might not qualify.)

                                                Click here to see the answer.

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},