Datadictionary

What is a datadictionary?
What should be included in a datadictionary?
Who should have access to a datadictionary?
How do I create a datadictionary?
Show me an example of a datadictionary

What Is A Datadictionary?

What is a datadictionary?

A datadictionary, or data dictionary as used by some authors, is the repository of all design and maintenance information for a database. It is simultaneously the specification and documentation, or reference manual of the particular database.

What Should I Include?

What should be included in a datadictionary? At least the following...

• Logical data model, ER diagram, notes.
• Entity and Attribute definitions, data type, data domain, defaults, descriptions.
• Entity relationships, primary and foreign keys, cardinality, descriptions.
• Domain constraints, all data domain definitions used in the database.

In addition to these, a good datadictionary should also contain any additional information about the design, intended use and administration of the database, possibly including...

• Conceptual notes, how and why this database was created.
• User information, how users access and modify the database.
• Access controls, restrictions and enforcement mechanisms.
• Administrative notes, procedures, tips, other info accumulated during the life-cycle of the database.
• To-Do list, design and implementation to-do notes and checklist.
• Anything else that will be helpful to long term maintenance of the database.

Who Should Have Access?

Who should have access to the datadictionary?

A useful datadictionary is essential to the success of any database project, and ease of access is central to being useful!

So, the answer to "Who should have access?" is everyone that has a need for access! Some information such as information about access control itself should obviously be restricted to certain people, but in general, everyone that has a function related to design, administration and direct use of the database should have ready access to the datadictionary.

Conversely, users insulated from direct use of the database, (ie. those who access it only through forms or user views) usually should not have access to the datadictionary, although there may be exceptions.

In an ordinary business or network environment this usually means that the datadictionary should be available as HTML pages viewable with any web browser, possibly with password protection.

Importantly, access to the datadictionary should not require use of any special software or access to the actual database design or administration tools! Remember, the datadictionary provides documentation, not implementation.

How Do I Create A Datadictionary?

How do I create a datadictionary?

A datadictionary can take several forms from a paper notebook to a commercial software application. You should make use of whatever format is appropriate to your application and work environment.

When we talk about databases we are almost always talking about computer based systems. So it is assumed that you have access to at least a simple word processor or other documentation tools. Any of these can be used to create a datadictionary for simple designs.

Most database designers will use some form of design tools. Most of these include report generation functions. Well planned reports (with consistent formatting) can become an important part of a datadictionary - learn to use them!

Finally, pencil and paper remain one of the best tools for the imaginative - use them too! But be sure to make any valuable results available to others by scanning, reproducing or at least making note of them in your electronic datadictionary.

Remember: The datadictionary is both the specification and documentation of your database, organize it, maintain it and make use of it with that in mind!