Develops an approach for advance estimation of user charges based on information actually retrieved by searching numeric databases, and defines a method for query cardinality estimation. Based on the relational data model, which uses relational algebra, this method uses formal file descriptions to describe the database files. (LRW)

The resolution power of a key is its ability, in the context of other keys for a given request, to increase query performance. This article studies the statistical properties of search keys, methods of characterizing the resolution power of keys automatically, and effects keys of varying resolution power have on retrieval effectiveness. (AEF)