Assume that you use business rules in Master Data Services (MDS) of Microsoft SQL Server 2012 or SQL Server 2014. When a business rule sets an attribute value to blank, it sets the blank value to a NULL value on the database side. In this situation, when another business rule evaluates whether the attribute is blank, it does not equate a NULL value with a blank value.
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To work around this issue, append checking condition "OR Attribute is equal to ~NULL~" in the business rule when you evaluate whether an attribute is blank.
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.