1. A method of converting a document corpus containing an ordered plurality of documents into a compact representation in memory of occurrence data, said representation to be based on a dictionary previously developed for said document corpus and wherein each term in said dictionary has associated therewith a corresponding unique integer, said method comprising: developing a first vector for said entire document corpus, said first vector being a listing of said unique integers corresponding to dictionary terms such that each said document in said document corpus is sequentially represented in said listing; and developing a second vector for said entire document corpus, said second vector indicating the location of each said document's representation in said first vector.