A methodology for user charge estimation in numeric online databanks. Part I: A review of numeric databanks and charging principles

Abstract

Recent studies on user charging in information retrieval services emphasize charging on the basis of the information retrieved from the databases or its retrieval costs as being more justified and appropriate as bases for charging than the tradi tional connect-time. When these charging bases are apphed in numeric online databanks, the charges vary over a very broad range, depending on factors which the users cannot know or manage. Therefore the users cannot estimate their charges in advance, prior to query execution. This has many undesirable practical consequences on information retrieval and informa tion seeking. In order to avoid such consequences and to achieve full advantage of such charging bases, user charge estimation tools which automatically estimate the charges on the basis of user query statements must be provided in the query systems to databanks. A novel and systematic methodol ogy for user charge estimation, to be applied by the tools, is reviewed. The methodology has been developed in the context of the relational data model. By applying the methodology, user charges for the information retrieved and its retneval costs for relational algebra quenes can be estimated generally, accu rately and conveniently. In addition to the charge estimates, the methodology provides rich descriptions of the query results that essentially support query formulation. Therefore the user can concentrate on query formulation with a clear idea about the query result and his charges in mind. The architecture of the methodology is such that the methodology can be extented to further charging bases in information retneval (e.g. data communication costs). In the article, the state of the art and trends in the development and use of databanks and in the charging principles of information retrieval are first reviewed. The methodology is then descnbed and special attention is paid to the design of user interfaces of the tools based on the methodology.