Domain

Domain refers to the complete set of possible values that can be assigned to an attribute. It standardizes the characteristics of attributes within a logical or physical data model.

For instance, a Date domain includes all valid date values and can be used for date-related attributes, such as EmployeeHireDate, OrderEntryDate, ClaimSubmitDate, or CourseStartDate.

Types of Domains

• Data Type Domain: Specifies the standard types of data an attribute can have, such as:

  • Integer
  • Character(30)
  • Date

• Data Format Domain: Uses patterns or templates to define valid values. This can include:

  • Postal codes
  • Phone numbers
  • Character limitations (e.g., alphanumeric, special characters)

• List Domain: Contains a finite set of predefined values, similar to dropdown lists. For example:

  • OrderStatusCode can be restricted to values like Open, Shipped, Closed, Returned.

• Range Domain: Specifies a range of acceptable values for a data type, which can be open-ended. For example:

  • OrderDeliveryDate must be between OrderDate and three months in the future.

• Rule-based Domain: Defined by rules that ensure the validity of values by comparing them to calculated values or other attributes. For example:

  • ItemPrice must be greater than ItemCost.

Domains provide a structured way to ensure consistency and integrity across data models by restricting the values that can be assigned to specific attributes.