Data dictionary

It provides the information stored in it to the user and the DBA, but it is mainly accessed by the various software modules of the DBMS itself, such as DDL and DML compilers, the query optimiser, the transaction processor, report generators, and the constraint enforcer.

[3] This typically includes the names and descriptions of various tables (records or entities) and their contents (fields) plus additional details, like the type and length of each data element.

The data dictionary consists of record types (tables) created in the database by systems generated command files, tailored for each supported back-end DBMS.

For example, a high-level data dictionary can provide alternative entity-relationship models tailored to suit different applications that share a common database.

For example, PHPLens includes a PHP class library to automate the creation of tables, indexes, and foreign key constraints portably for multiple databases.

[8] Visual DataFlex features[9] provides the ability to use DataDictionaries as class files to form middle layer between the user interface and the underlying database.

The real estate industry, for example, abides by a RESO's Data Dictionary to which the National Association of REALTORS mandates[10] its MLSs comply with through its policy handbook.

[11] This intermediate mapping layer for MLSs' native databases is supported by software companies which provide API services to MLS organizations.