Data Management Capabilities > Managing Part Structures > Windchill Options and Variants Capabilities > Developing Advanced Selection Logic for Configurable Modules > Basic Steps for Defining Advanced Selection > Adding a Constraint
Adding a Constraint
Adding a constraint allows you to specify a condition for a configurable module. A constraint can be simple, consisting of only one part, or can be more complex, consisting of multiple parts.
To add a constraint:
1. In the Part Structure Browser, select the configurable module for which you want to add a constraint.
2. Click the Constraints tab.
3. Click in an empty row to add a constraint.
4. Select the constraint type from the drop-down list: Case Table, Expression, or External Application.
5. Type the name to identify the expression.
6. Define the constraint:
If you have specified a Case Table constraint type, the Case Table Editor is displayed in the pane below.
If you have specified an Expression constraint type, the Expression Editor is displayed in the pane below. You can either type the expression in the Expression field, or use the selections available in the Expression Editor to form the expression.
If you have specified an External Application constraint type, the External Application Configuration Editor is displayed in the pane below.
7. (Optional) Type any identifying alert text for the expression. The Alert shows this message if the constraint is violated. If you do not specify the alert message, violation of the constraint produces an automatically generated message, which lists the expression that defines the constraint.
You can also add constraints within the same configurable module using copy and paste. This functionality is not available for copying constraints from one configurable module to another.