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Data dictionaries are created during the design phase to define the structure of a database.

Creating relational database management systems can be time consuming, and a data dictionary will act as an efficient reference point during implementation.

Data dictionaries contain the following metadata.

• name of each entity
• name of all attributes associated with each entity
• type of data that will be held by each attribute
• size of each attribute (taking account of the overall file size to be held in RAM or backing storage)
• indication of attributes that will be used as primary or foreign keys during implementation
• validation rules that are to be applied to attributes

At Higher level, you are expected to describe and exemplify a data dictionary with three or more entities.