Revisiting dictionary-based compression

An attractive way to increase text compression is to replace words with references to a text dictionary given in advance. Although there exist a few works in this area, they do not fully exploit the compression possibilities or consider alternative preprocessing variants for various compressors in the latter phase. In this paper, we discuss several aspects of dictionary-based compression, including compact dictionary representation, and present a PPM/BWCA-oriented scheme, word replacing transformation, achieving compression ratios higher by 2-6% than the state-of-the-art StarNT (2003) text preprocessor, working at a greater speed. We also present an alternative scheme designed for LZ77 compressors, with the advantage over StarNT of reaching up to 14% in combination with gzip. Copyright (c) 2005 John Wiley & Sons, Ltd.