1. A method for searching a corpus of documents, comprising: defining a knowledge domain; identifying a set of reference documents in the corpus pertinent to the domain; inputting a first query; searching the corpus using the set of reference documents to find one or more of the documents in the corpus that contain information in the domain relevant to the first query; and adding at least one of the found documents to the set of reference documents for use in searching the corpus for information in the domain relevant to a second, subsequent query.