Allowed References
Use the Allowed References node () to define a model entity list for the parent Feature Input. The Settings window of this node contains the following sections:
Definition
From the Reference list, choose one for the following options:
•
 Feature list (the default) for the physics features as the siblings to this feature.
•
 Parent feature list for the siblings to the parent feature
•
 Physics feature list for the physics features.
•
 Physics list for the physics.
•
 Multiphysics list for the multiphysics coupling features.
•
 Coordinate system list for the coordinate systems in the model.
•
 Material list for the materials.
•
 Function list for the functions.
•
 Common feature list for the common features.
•
 Extra dimension list for the extra dimension features.
•
Child list of reference input for the child list of the selected entity by another reference input. To specify the controlled reference input for this list, you can then choose, from the Specify reference input list, By reference (the default) or By name. If you choose By name, you can choose one of the following options from the From list: User input from this feature, Parent feature, This feature or any ancestor, or User input from this property. For the last option, specify the property in the Property field. Select a reference input from the Reference list (if specified by reference) or type it in the Reference field (if specified by name).
From the Filter list, for most options, only User defined can be chosen. Then define the filtering using the Filtering types list (see below). The Material list has two predefined filters: Layered materials and Porous materials.
The  list can be filtered by adding a type to the Filtering types list. A type is, for example, a physics feature ID. The filtering type also supports regular expressions and defining a subfeature list type as, for example, FeatID/SubFeatID.
The filtering can also be done by selecting the Use condition on list check box and then add a condition. For example, a condition that states that a user input in the features in the list should have a certain value.
Activation Condition
Enable the condition by selecting the Use condition check box. The activation condition can depend on user inputs in the parent feature, parent property, or some property. If the user input is under a feature or property, which can contain other user inputs, you can directly refer to any of those user inputs by choosing By reference in the Specify user input list. You then choose the user input from the User input list, and finally add or enter the values that activates the user input in the Activating values list. This list differs depending on the user input you refer to.
Select the Invert condition on input values check box to invert (negate) the condition.
When the Require input is active check box is selected, the activation condition is only true if the checked user input is also active as decided by its activation conditions. It is only applicable when specifying a user input to check by reference or by name, not for expressions. For expressions, you can achieve the equivalent logic using the isActive operator.