This chapter discusses these forms of the logical schema and also shows how the data structures might be described to the database.

Indeed the means by which record occurrences are related physically is irrelevant to the logical schema.

Its format may also be different from the logical schema.

But whatever the description given to the user, the underlying data described by the logical schema will be the same.

But applications must provide a logical schema that defines how the file format should be interpreted.

A logical schema is a data model of a specific problem domain expressed in terms of a particular data management technology.

The physical schema is a particular implementation of a logical schema.

This eliminates the need to normalize data sets in the logical schema.

The logical schema was the way data were represented to conform to the constraints of a particular approach to database management.

Describing the logical schema, however, still did not describe how physically data would be stored on disk drives.