Compressed text databases with efficient query algorithms based on the compressed suffix array

A compressed text database based on the compressed suffix array is proposed. The compressed suffix array of Grossi and Vitter occupies only O(n) bits for a text of length n; however it also uses the text itself that occupies O(n log \Sigma\) bits for the alphabet Sigma. On the other hand, our data structure does not use the text itself, and supports important operations for text databases: inverse, search and decompress. Our algorithms can find occ occurrences of any substring P of the text in O(\P\ log n + occ log(epsilon) n) time and decompress a part of the text of length l in O(l + log(epsilon) n) time for any given 1 greater than or equal to epsilon > 0. Our data structure occupies only n(2/epsilon (3/2 + H-o + 2 log H-o) + 2 + 4 log(epsilon) n/log(epsilon) n-1)+o(n)+O(\Sigma\ log\Sigma\) bits Where H-o less than or equal to log \Sigma\ is the order-0 entropy of the text. We also show the relationship with the opportunistic data structure of Ferragina and Manzini.