Abstract: Ziv-Lempel-type compression and expansion using separate static compression and expansion dictionaries as opposed to a single adaptive dictionary. The static dictionaries make random access processes usable for short data records instead of only long sequential data streams. Degree of compression and compression performance are improved by allowance of multiple extension characters per node and multiple children, of the same parent, that have the same first extension character. Performance is further improved by searching for matches on children of a parent and detecting a last possible match by means of fields in the parent instead of by accessing the children. Expansion performance is improved by representing in an entry not only the extension character or characters of the entry but also those of some number of ancestors of the entry, thus avoiding accessing the ancestors.