1. A method for identifying an expert information source, the method comprising: analyzing first search results obtained by a search system, the first search results including search results for at least one query associated with more than one category included in a query ontology; based on the analysis of the first search results, determining a relative contribution by an information source to the first search results; analyzing second search results, obtained by the search system, for queries associated with a particular category included in the query ontology, the second search results being different but not exclusive of the first search results; based on the analysis of the second search results, determining a relative contribution by the information source to the second search results; comparing the relative contribution by the information source to the first search results to the relative contribution by the information source to the second search results; based on comparison results, determining whether the relative contribution by the information source to the second search results is more than a threshold greater than the relative contribution by the information source to the first search results; and in response to determining that the relative contribution by the information source to the second search results is more than the threshold greater than the relative contribution by the information source to the first search results: identifying the information source as an expert information source for the particular category included in the query ontology; and storing, in electronic storage, data indicating that the information source is an expert information source for the particular category included in the query ontology.