19. A method comprising: generating, by a computing device, a search query based upon search terms extracted from a question in response to receipt of the question from an invoker; adding, by the computing device, at least one restricting term to the search query, the at least one restricting term based upon a category associated with the question and comprising a site scope modifier to restrict the query to at least one web site associated with the category, the site scope modifier specifying the at least one web site to which the query is restricted; selecting, by the computing device, the at least one web site associated with the category from a mapping table that associates the at least one web site with the category, the mapping table specific to a type of online forum; conducting, by the computing device, a search for computer-readable documents that match the search query; and sending, by the computing device, to the invoker at least one link produced by the search, wherein the at least one link comprises at least one reference to at least one document that matches the search query.
19. A method comprising: generating, by a computing device, a search query based upon search terms extracted from a question in response to receipt of the question from an invoker; adding, by the computing device, at least one restricting term to the search query, the at least one restricting term based upon a category associated with the question and comprising a site scope modifier to restrict the query to at least one web site associated with the category, the site scope modifier specifying the at least one web site to which the query is restricted; selecting, by the computing device, the at least one web site associated with the category from a mapping table that associates the at least one web site with the category, the mapping table specific to a type of online forum; conducting, by the computing device, a search for computer-readable documents that match the search query; and sending, by the computing device, to the invoker at least one link produced by the search, wherein the at least one link comprises at least one reference to at least one document that matches the search query. 21. The method of claim 19 , wherein generating a search query comprises forming a disjunction of multiple search terms in response to the at least one search term comprising multiple search terms.