Data Dictionary

Every database should have a data dictionary. A data dictionary is a file that defines the basic organization of a database. It contains a collection of data element definitions in the database. More advanced data dictionary contains database schema with reference keys, still more advanced data dictionary contains entity-relationship model of the data elements or objects. Data dictionaries do not contain any actual data from the database, only bookkeeping information for managing it. The contents

1. Data element definitions
2. Table definitions
3. Database schema
4. Entity-relationship model of data
5. Database security model