DATA-COMPRESSION IN FULL-TEXT RETRIEVAL-SYSTEMS

When data compression is applied to full-text retrieval systems, intricate relationships emerge between the amount of compression, access speed, and computing resources required. We propose compression methods, and explore corresponding tradeoffs, for all components of static full-text systems such as text databases on CD-ROM. These components include lexical indexes, inverted files, bitmaps, signature files, and the main text itself. Results are reported on the application of the methods to several substantial full-text databases, and show that a large, unindexed text can be stored, along with indexes that facilitate fast searching, in less than half its original size-at some appreciable cost in primary memory requirements.