Definition:
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'.
|
yes | required item in this category of looped list |
|
no | optional item in this category of looped list |
Type: char
Category: list
Copyright © 2005 International Union of Crystallography