Data Management Capabilities > Managing Part Structures > Windchill Options and Variants Capabilities > Assigning Expressions > Supported Expressions
  
Supported Expressions
If the Platform Structures module is installed, an administrator can set a preference to specify the type of expressions to use for defining optionality in a configurable product structure. The Windchill preference Supported Expressions (located in the Options and Variants section of the Preference Management utility) has the following values:
Basic expressions only
Advanced expressions only
Both basic and advanced expressions
* 
Although both types of expressions can be created in the product structure when the preference is set to Both basic and advanced expressions, only one type can be assigned to an item.
You can set this preference for a site, organization, product, or library.