data dictionary

database A data structure that stores meta-data, i.e. data

about data. The term "data dictionary" has several uses.

Most generally it is a set of data descriptions that

can be shared by several applications.

Usually it means a table in a database that stores the

names, field types, length, and other characteristics of

the fields in the database tables.

An active data dictionary is automatically updated as changes

occur in the database. A passive data dictionary must be

manually updated.

In a DBMS, this functionality is performed by the systemcatalog. The data dictionary is a more general software

utility used by designers, users, and administrators for

information resource management.

The data dictionary may maintain information on system

hardware, software, documentation, users, and other aspects.

Data dictionaries are also used to document the database

design process itself and can accumulate meta-data

ready to feed into the system catalog.

[Does anybody call them "codebooks"?]

(2001-04-24)