10. A method for defining a content relevance model for a particular category, the method comprising: identifying a set of key word sets for the particular category based on an analysis of (i) a first set of content segments previously defined as relevant to the particular category and (ii) a second set of content segments previously defined as not relevant to the particular category; identifying (i) a set of pairs of word sets that each comprise a key word set and a word set that appears in a defined context of the key word set and (ii) a score for each of the word set pairs, the score for a particular word set pair quantifying a likelihood that a content segment containing the particular word set pair is relevant to the particular category, wherein appearances of the particular word set pair in the first set of content segments increase the score for the particular word set pair and appearances of the particular word set pair in the second set of content segments decrease the score for the particular word set pair; and defining a content relevance model for the particular category, the content relevance model comprising (i) a context definition that indicates when a second word set appears within a context of a key word set and (ii) the set of word set pairs and corresponding scores.
10. A method for defining a content relevance model for a particular category, the method comprising: identifying a set of key word sets for the particular category based on an analysis of (i) a first set of content segments previously defined as relevant to the particular category and (ii) a second set of content segments previously defined as not relevant to the particular category; identifying (i) a set of pairs of word sets that each comprise a key word set and a word set that appears in a defined context of the key word set and (ii) a score for each of the word set pairs, the score for a particular word set pair quantifying a likelihood that a content segment containing the particular word set pair is relevant to the particular category, wherein appearances of the particular word set pair in the first set of content segments increase the score for the particular word set pair and appearances of the particular word set pair in the second set of content segments decrease the score for the particular word set pair; and defining a content relevance model for the particular category, the content relevance model comprising (i) a context definition that indicates when a second word set appears within a context of a key word set and (ii) the set of word set pairs and corresponding scores. 11. The method of claim 10 , wherein the defined context of a key word set is a context defined for the content relevance model.