1. A computer-readable storage medium storing computer-executable instructions that, when executed, cause one or more processors to perform acts comprising: preparing a new domain to receive classification knowledge from one or more source domains by populating the new domain with preliminary query patterns extracted from a search engine log; preparing the classification knowledge in at least one source domain for transfer to the new domain; and transferring the classification knowledge from one or more source domains to the new domain, the transferring comprising: computing similarity distances between a plurality of source domains and the new domain; discarding at least one of the plurality of source domains with a similarity distance that is greater than a predefined distance threshold to generate the one or more source domains; selecting one or more query patterns of the one or more source domains for the new domain based at least on consistency between the one or more query patterns and the preliminary query patterns; and transferring the one or more query patterns that are selected to the new domain.