20. The computer-readable memory device of claim 15 , where the generated score is a first score and the one or more instructions further cause the at least one processor to: generate a second score, for the document, that is based on a relevance of the document to a search query; and combine the first and second scores to generate an overall score, where the one or more instructions to rank the document further cause the at least one processor to: rank the document with regard to the at least one other document based on the overall score.
15. A non-transitory computer-readable memory device comprising: one or more instructions which, when executed by at least one processor, cause the at least one processor to: determine, at a first time, a first set of topics relating to content within a document; determine, at a second time, a second set of topics relating to the content within the document, the second time being different than the first time; identify a change in a quantity of topics between the first set of topics and the second set of topics; generate a score for the document based on the change in the quantity of topics; and rank the document with regard to at least one other document based on the score.