DDL dictionary version 1.4.1
Signals whether the defined item must be present in the loop structure containing other items of the designated _category. This property is transferrable to another data item which is identified by _related_item and has _related_function set as 'alternate'.
The data value must be one of the following:
|required item in this category of looped list|
|optional item in this category of looped list|
Enumeration default: no