One general aspect is described that includes a computer implemented method for generating a pattern graph. The method may include accessing data pertaining to a corpus of web documents. The data may include a plurality of query-document pairs. The method may also include identifying at least one query pattern in the plurality of query-document pairs and the query pattern may be associated with a portion of web documents in the corpus. The method may also include identifying a plurality of sub-phrases in the at least one query pattern, determining, in the corpus of web documents, a plurality of other query patterns that include at least one of the plurality of sub-phrases, and assigning an classifier to the at least one query pattern and each of the plurality of other query patterns that include at least one of the sub-phrases.