Data Description Language (DDL)
Loosely, the section of a database management system concerned with the specification of the logical structure of the data;
specifically, the language used for that purpose. In early database systems
little distinction was made between the logical and physical structure of the
data, and the DDL usually contained information concerning both. It is becoming
increasingly common for these two aspects to be separated, and for the DDL to be
restricted to the logical structure while information concerning
the physical data structure is contained in a data structure language.