In light of the current state of the networks in the Instrument & Control Company an electronic document signing system of ASP-based local networks has been developed and the management efficiency of the Company has been accordingly improved and therefore the conditions for automatic office work can be realized in the Company.

This paper reviews the recent researches on this topic, which include the main techniques such as inverted files, signature files, suffix trees, suffix arrays, compressed indices based on the indices mentioned above, self-index based on inverted files, and self-index based on suffix arrays.