Don't ‘have a clue’? Unsupervised co-learning of downward-entailing operators.

Cristian Danescu-Niculescu-Mizil and Lillian Lee

Proceedings of ACL, 2010. Short paper.

PDF (with appendices)

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:                Without a ‘doubt’



Researchers in textual entailment have begun to consider inferences involving downward-entailing operators, an interesting and important class of lexical items that change the way inferences are made. Recent work proposed a method for learning English downward-entailing operators that requires access to a high-quality collection of negative polarity items (NPIs).  However, English is one of the very few languages for which such a list exists.  We propose the first approach that can be applied to the many languages for which there is no pre-existing hight-precision database of NPIs.  As a case study, we apply our method to Romanian and show that our method yields good results.  Also, we perform a cross-linguistic analysis that suggests interesting connections to some findings in linguistic typology.




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

  title={Don't `have a clue’? {Unsupervised} co-learning of downward-entailing


  booktitle={Proceedings of ACL},



  annote={Short paper}