What is the purpose of a data dictionary?

• A. Store passwords for data elements.
• B. Describe business processes unrelated to data.
• C. Log all user actions performed on data.
• D. Document metadata for data elements: definitions, data types, allowed values, relationships, owners, and business rules.

Answer: (D)

A data dictionary is a centralized catalog of metadata about data elements. It defines what each data item means, its data type, valid values or domains, any relationships to other data, who owns or is responsible for it, and the business rules or constraints that apply. This makes data usage consistent across the organization, supports data governance, and helps developers, analysts, and data stewards understand and validate data correctly. For example, a data element like customer_id would specify that it’s an integer, its length or range, that it’s the primary key in the customers table, must be unique and not null, who the data steward is, and how it relates to other tables such as orders or invoices through foreign keys.

Storing passwords is a security-related task rather than documenting data meanings. Describing business processes unrelated to data misses the focus on data definitions and rules. Logging all user actions on data relates to auditing and activity tracking, not documenting what data items mean and how they should be used.