A business rule in Master Data Services is a rule that you employ to ensure the quality and accuracy of your master data.
Is it feasible to create a business rule to verify that the value for a combination of columns (Composite key) is unique?

Solution
Navigate to Administrative Tasks on the Master Data Service (MDS) site.

Click on Manage >> Business Rules

Select the Model and Entity within which you need to add the Business Rule. And Click on Add.

Provide the Name and Description for the Business Key and Click on Add section within Then

Select the Attribute ( one column ) and Operator as : Must be Unique in Combination with the following attributes.

Post that select the other Columns which are part of Composite key (other columns that needs to be added as part of uniqueness) and Click Add.

Finally, Click on Save.
Click on Save to Create the Business Rule.

The Business Rule would be in Activation Pending State

To Activate it, Click on Publish All.

Post this, the Business Rule would in Active state:

Output
Composite Key is Unique

Composite Key is Duplicate

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