Data Dictionary as a Metadata Repository



Metadata is “data that provides information about other data”. In short, it’s data about data.

Source: Wikipedia


Database Schema

The database schema of a database is its structure described in a formal language supported by the database management system (DBMS). The term “schema” refers to the organization of data as a blueprint of how the database is constructed (divided into database tables in the case of relational databases).

Source: Wikipedia

A database generally stores its schema in a data dictionary. (Wikipedia)

Snowflake Schema


Source: Wikipedia

XML Schema


Source: Wikipedia

Data Dictionary

A data dictionary is used to standardize a definition of a data element and enable
a common interpretation of data elements.

A data dictionary is used to documentstandard definitions of data elements, their
meanings, and allowable values. A data dictionary contains definitions of each
data element and indicates how those elements combine into composite data
elements. Data dictionaries are used to standardize usage and meanings of data
elements between solutions and between stakeholders.

Data dictionaries are sometimes referred to as metadata repositories and are used
to manage the data within the context of a solution. As organizations adopt data
mining and more advanced analytics, a data dictionary may provide the metadata
required by these more complex scenarios. A data dictionary is often used in
conjunction with an entity relationship diagram (see Data Modelling (p. 256)) and
may be extracted from a data model.

Data dictionaries can be maintained manually (as a spreadsheet) or via automated



  • Metadata is data about data. It’s not the data itself.
  • Schema is one type of metadata that describes how the data is organized.
  • Data Dictionary details may include definitions, relationships with other data, origin, format, and usage.
  • A data dictionary is a collection of metadata conceptually and a repository of metadata physically.

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