Illustration is made on requirements of the system's user to define precisely his subject and purpose of search as well as short summary of them and to feed back his comments on the result of the search into the system for easier approach to a final query formulation. The introduction of the two parameters added to the well-known is likely to give a helpful solution in transforming a query by loosening or tightening. Following explanation of the retrieval prognosis formula, represented is a principle in preparation of a retrieval prognosis nomogram as well as two examples of the use of it. Thesaurus size is made clear to depend on the collection size and type of user's needs too. An overall estimate of the system indicates to keep a balance among the average figures of key parameters concerned in the output and input.