10. The method of claim 1 , wherein accessing data indicating the set of classes comprises accessing data indicating a hierarchy of classes corresponding to the particular semantic concept, wherein at least some of the classes in the hierarchy represent different forms of expressing at least a portion of the particular semantic concept.
10. The method of claim 1 , wherein accessing data indicating the set of classes comprises accessing data indicating a hierarchy of classes corresponding to the particular semantic concept, wherein at least some of the classes in the hierarchy represent different forms of expressing at least a portion of the particular semantic concept. 12. The method of claim 10 , wherein the first class and the multiple second classes are located at different levels of the hierarchy, and the multiple second classes are sub-classes of the first class.