US Patent 9444772 Social search engine

Methods, systems, and apparatus, including computer programs encoded on a computer storage medium, for a social search engine. In one aspect, a method includes receiving a question from an asker in which the question is associated with one or more topics; selecting candidate answerers based at least partly on each answerer's respective relationship to the asker; sending the question successively to groups of one or more candidate answerers according to the ranking until an answer is received from a particular one of the candidate answerers; and sending to the asker the received answer and information that identifies the particular answerer.