Ranked document retrieval for multiple patterns.

Let D={T1,T2,…,TD} be a collection of D documents having n characters in total. Given two patterns P and Q, and an integer k>0, we consider the following queries.•top-k forbidden pattern query: Among all documents containing P, but not Q, report the k documents most relevant to P.•top-k two pattern query: Among all documents that contain both P and Q, report the k documents most relevant to P.