http://jeudi.inrialpes.fr/2007/Raweb/talaris/uid25.html
In essence, the textual entailment recognition task is an inference task, namely deciding whether the information contained in a given text T1can be inferred from the information provided by another text T2.
It is crucial to be able to answer this question. One important characteristic of natural language is the large number of ways in which it can express the same information. Many natural language processing applications like question answering, information retrieval, generation, and anaphora resolution need to deal with this diversity efficiently and accurately, and recognising textual entailments is a key step towards this.
Textual entailment recognition is a difficult task. The approach we are experimenting with is to encode lexical information as a description logic ontology (or a hybrid logic theory) and then to use logical inference to compute the result.