Through the example of Tongji Information Retrieval Network System (TJIRNS), the paper mainly describes on-line expansion function and its implementation under the specific conditions.

As an exsmple, the design idea and the implementation of the on line microimage retrieval system of academic journals in Sichuan university are described in details.

This paper describes a multi-user on-line retrieval system, which was developed and used to process library document information in people's university.