Yes, Tom may wish to look up
author = "W. B. Frakes and R. S. Baeza-Yates",
title = "Information Retrieval: Data Structures and Algorithms",
publisher = "Prentice Hall",
year = 1992}
Look for terms such as Pat-trees and Pat-arrays as well.
-- Raman Chandrasekar, CASI/Instt for Research in Cognitive Science, Univ of Pennsylvania,3401 Walnut St, Suite 400A, Philadelphia PA 19104 Phone: +1-215-898-0332, Fax: +1-215-573-9247, Home: +1-610-352-5512 email@example.com http://www.cis.upenn.edu/~mickeyc/