  In this paper we present a general method for information extraction that
exploits the features of data compression techniques. We first define and focus
our attention on the so-called "dictionary" of a sequence. Dictionaries are
intrinsically interesting and a study of their features can be of great
usefulness to investigate the properties of the sequences they have been
extracted from (e.g. DNA strings). We then describe a procedure of string
comparison between dictionary-created sequences (or "artificial texts") that
gives very good results in several contexts. We finally present some results on
self-consistent classification problems.
