Incremental data compression -extended abstract-

Abstract

Data may be compressed using textual substitution. Textual substitution identifies repeated substrings and replaces some or all substrings by pointers to another copy. We construct an incremental algorithm for a specific textual substitution method: coding a text with respect to a dictionary. With this incremental algorithm it is possible to combine two coded texts in constant time. Furthermore, the time required for deleting or inserting a piece of text and coding the resluting text is linearly dependent on the length of the deleted or inserted piece of text. The algorithm is constructed by means of a theory of incremental algorithms on the datatype list, based on the Bird-Meertens calculus for program transformation. The algorithm consists of several parts that correspond to the edit actions available on the datatype list. The most important part of the algorithm is the part that combines two coded texts, which is essentially a dynamic programming algorithm.