Currently there is a big thrust towards the development of automated, user-friendly online information retrieval systems, which are software packages that allow a user population to query and receive appropriate information that is stored in a computer data-base. Our research adopts a knowledge based approach to the design and development of KADRE (Knowledge Assisted Document Retrieval Expert),
... [Show full abstract] an experimental online document retrieval system. Knowledge based techniques allow us to incorporate some of an expert librarian's heuristic techniques into the retrieval process. We present the mathematical model of the retrieval system as a five step process and discuss the system thesaurus in some detail. Six different transitive closures of the relational matrix of term pairs are used to compute the thesaurus, and the retrieval output produced by these techniques are compared. Representation of the thesaurus as a transitive closure offers two very significant advan-tages: this method provides a means for completion of partial knowledge which is represented as numerical relational data; and the ensuing completion has a well defined property of (mathemati-cal) consistency.