Data definition language <language, database> (DDL) 1. A language enabling the structure and instances of a {database} to be defined in a human-, and machine-readable form. {SQL} contains DDL commands that can be used either interactively, or within programming language {source code}, to define databases and their components, e.g. CREATE and DROP. See also {Data manipulation language} (DML). 2. A specification language for databases, based on the {entity-relationship model}. It is used in the {Eli} {compiler-compiler} to manage type definitions. ["DDL Reference Manual", ECE Dept U Colorado, 1991]. (1999-04-26)