An approach to query cost modelling in numeric databases
Kalervo Järvelin · Journal of the American Society for Information Science · 1989
Numeric online 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 charging policy for all online IR have been based on charging either for information actually retrieved from the database or for the costs of processing user queries rather than for the connect-time. However, the viability of such charging schemes depends totally on the user's possibilities of estimating the charges in advance, during the query negotiation phase. Due to the complexity of the modern database management systems (DBMS), users cannot estimate such charges in advance without cost estimation tools. In this article, user charges based on query processing costs in NDBs are considered and the problem of estimating such charges in advance is analyzed. A systematic and general approach with many desirable properties is proposed to query cost estimation. The approach is based on the well-known relational data model (RDM) and the query optimization, cardinality estimation and file design techniques developed in this context. Tools based on the approach are necessary components of query interfaces to NDBs if a mode of charging not based on connect-time is used. © 1989 John Wiley & Sons, Inc.