Each of these tasks focuses, however, on a different level of linguistic analysis from ours: Following the definitions embraced by Recasens and Vila (2010), "paraphrasing" is a relation between two lexical units that have the same meaning, whereas "coreference" indicates that two referential expressions point to the same referent in discourse.
3 to work on paraphrasing, we are specifically interested in pairs of text fragments that involve implicit arguments, which can only be resolved in context.