Data Dictionaries are metadata repositories. They don’t hold the data, they hold the information that describe the data. They are composed of names and descriptions of the various tables of your Relational Databases, and often the relationships between them (like in an Entity-Relationship Diagrams). Having a data dictionary is a good thing, even better when you can marry them in with Data Flow Diagrams or other types of Diagrams.
Data Dictionaries can be active or passive. Passive data dictionaries are essentially static representations of the database. Active data dictionaries are capable of self-updating on database changes and/or imposing constraints on the data stored (e.g. “this int field only goes from 0 to 10”).
Typical Attributes
Each field would have associated with these meta-data attributes:
- Group Name
- Name
- Displayed Title
- Type
- Constraints (e.g. max/min, decimal place count)
- Default value
- Prompt type
- Is required
- Is read only
- Is unique
- Event-driven handlers (e.g. “on-click” routines)
- Formatting info
- Description