Which data management language component enables the DBA to define the schema…

Concept

A database language is split by what it acts on. A Data Definition Language (DDL) declares structure — its statements are compiled and stored in the data dictionary (system catalogue) and no data value is touched. A Data Manipulation Language (DML) acts on the occurrences stored inside that structure.

DDL is then split again by the level of the ANSI/SPARC three-level architecture it describes: the schema DDL describes the conceptual (global logical) level, and the sub-schema DDL describes the external level — one view per application program.

Application

1. The stem asks for the component that lets the DBA define the schema components — the record types, data items, keys and inter-record relationships that make up the database as a whole.

2. Those items belong to the conceptual level, and the language that declares the conceptual level is the schema DDL.

3. The DBA owns the conceptual level, so the schema DDL is the DBA’s tool, and its compiled output is what the data dictionary records.

4. Hence the component is the schema DDL (Data Definition Language for the schema).

Cross-check

Map each named component onto the level it belongs to:

• DML declares nothing at all, so it cannot create a record type or a key.

• The sub-schema DDL only carves a view out of a schema that must already exist; it is the application programmer’s level, not the definition of the schema itself.

• "All of these" therefore fails: the three components sit at different levels and only one of them defines the schema.

Note on the printed paper

The original 2010 paper prints "DLL" in two of the options; this is a well-known typographical error for DDL (Data Definition Language). It has been corrected here so the options read as intended.