Description and performance analysis of signature file methods for office filing

Abstract

Signature files have attracted a lot of interest as an access method for text and specifically for messages in the office environment. Messages are stored sequentially in the message file, whereas their hash-coded abstractions (signatures) are stored sequentially in the signature file. To answer a query, the signature file is examined first, and many nonqualifying messages are immediately rejected. In this paper we examine the problem of designing signature extraction methods and studying their performance. We describe two old methods, generalize another one, and propose a new method and its variation. We provide exact and approximate formulas for the dependency between the false drop probability and the signature size for all the methods, and we show that the proposed method (VBC) achieves approximately ten times smaller false drop probability than the old methods, whereas it is well suited for collections of documents with variable document sizes.