On the equivalence of data base schemas—a semantic approach to data translation

摘要

A notion of the equivalence of data is the basis for deriving a correct translation of data bases. The equivalence of data base states and data base schemas is defined. Since this definition can only be given with respect to the semantics of data, a short discussion of data base semantics is given. It is shown, how a semantic data model and data definition language (LDDL) can be used to construct a correct specification of a translation function. Finally, an example of the translation of a CODASYL data base schema to a relational data base schema is given.