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# Structured and Described Data

A fundamental feature of the database approach is that the database system does not only contain the data but also the complete definition and description of these data. These descriptions are basically details about the extent, the structure, the type and the format of all data and, additionally, the relationship between the data. This kind of stored data is called metadata ("data about data").
Metadata
is used by the DBMS software but also by applications like GIS and by users of databases. As DBMS software is not written for one specific database application the metadata
of a database is used to get information about the extent, the structure, etc. of it.

Structured Data:
  Data is called structured if it can be subdivided systematically and linked.

Following is a simple example how data can be described in a database.
Following is a simple example how data can be described in a database. Below there is a database table. Because of the structure of this table (first column = Forename, second column = Surname, third column = Postcode, forth column = City) it is known that a entry in the first column must be a forename (coded as string) and an entry in the third column must be a postcode (coded as number).

Example of an Database Table