14. The system of claim 11 , wherein the textual data comprises opinion data that is posted on the Internet.
11. A system comprising: one or more processors; memory storing computer-executable instructions that, when executed on the one or more processors, perform acts comprising: collecting textual data of a target domain; categorizing, by a target classifier associated with the target domain, the textual data according to sentiment using identifiers previously imported to the target classifier from a trained classifier associated with a source domain; and sending data for display in a user interface to present a summary of results that are based at least in part on the categorizing the textual data.