Modelling concepts for reasoning about access to knowledge

There is growing agreement about the usefulness of putting semantic database constraints into explicit form that can be manipulated by various database management programs. Indeed, this is a prerequisite for building intelligent database mediators. These are programs that perform the task of a good database analyst: to pose the most effective and easily processed queries to help solve a problem. Semantic query optimization is a technique to exploit semantic constraints for one aspect of intelligent database mediation: increasing retrieval efficiency. The technique is to use semantic constraints to transform a query into an equivalent one that can be processed more efficiently. Various kinds of semantic knowledge that can be used for this purpose are described.