A Straightforward Method for Advance Estimation of User Charges for Information in Numeric Databases

Abstract

It is generally recognised that numeric databases (NDBs) have become essential in information retrieval (IR). NDBs differ from traditional bibliographic databases (BDBs) with respect to their content, structural complexity, data manipulation capabilities, and the complexity of the user interfaces and user charging schemes. Recent trends in user interfaces and user charging for all online IR are towards charging for the information actually retrieved from the database rather than for the connect time. However, the viability of such charging schemes depends on the user's ability to estimate the charges in advance, during the query negotiation phase. This paper presents a systematic and general method for estimating user charges for retrieved information in advance, in the context of NDBs based on the relational data model (RDM). The method accepts relational algebra (RA) queries of any complexity, estimates the sizes of their results, and charges for them on the basis of the descriptions of the original database files. The method is a novel one and is directly applicable to any RDM‐based NDB. Tools based on the method are required in the query interfaces to NDBs in order to make query formulation and reformulation meaningful.