The specialized Control Link used to provide the connection between an ordered aggregation of Expressions and the target fields of a Feature_ID.
The expr_index field is a 1-based index into the ordered aggregation of Expressions, and is used to select the specific Expression that controls the value of Feature ID's ID field.
In order to do this, the data provider attaches a Feature ID Control Link to the Feature ID object, where the ID field's controlling Expression is a Variable. In this way, each Feature Model Instance provides a different ID for the Feature Node within the Model.
| SE_STRING | description; | (notes) |
|---|
| SE_UINT32 | expr_index; | (notes) |
|---|
A text description of what the Control_Link is for
index of the expression whose value controls the ID of the affected <Feature ID> object.