11. The method according to claim 1, wherein said simplex noun phrases are described by a user-specified pattern.
1. A method for identifying significant topics in a document comprising the steps of: extracting from said document a complete list of simplex noun phrases and corresponding heads that represent candidate significant topics of said document; clustering said simplex noun phrases into groups by said heads; and ranking said clustered simplex noun phrases by said heads in accordance with a significance measure to identify said significant topics of said document from said candidate significant topics.