1. A computer-implemented method for detecting inferences from documents, wherein the computer includes a processor, the method comprising: receiving one or more documents; extracting a first set of knowledge relevant to the documents; formulating one or more queries to one or more reference corpora based on the first set of knowledge; extracting a second set of knowledge from results received in response to the queries; and detecting an inference by producing a mapping relationship between at least one document and a piece of the second set of knowledge which is not within the first set of knowledge, wherein the mapping relationship indicates an inference from the documents.
8. The method of claim 1 , further comprising receiving a set of sensitive knowledge relevant to the documents; wherein the piece of the second set of knowledge mapped to the document is also within the set of sensitive knowledge; and wherein producing the mapping relationship comprises determining an intersection between the set of sensitive knowledge and the second set of knowledge.