1. One or more computer-readable media having computer-executable instructions embodied thereon that, when executed, facilitate a method of determining that a query is relevant to a category of information, the method comprising: associating a seed document with the category, wherein the seed document is trusted to be relevant to the category; receiving an identification of a query that was previously input to a search engine, wherein, when a search-result document was presented in response to the query, the search-result document was selected; determining that the search-result document matches the seed document; and based on the search-result document matching the seed document, inferring that the query is relevant to the category.