A window object with VOLATILE flag is only supposed to be visible, if the display date actually exists. Otherwise it is automatically hidden by FillWindow or AdjustView.

When is object data missing?
This might be the case, if

• a Slot doesn't exist
• a pointer or a function provides the value ZERO in the access path
• accessing the k-th collection element, although the collection contains less than k elements (this also returns ZERO).

With a function, it is possible to decide anywhere in the Access Path, whether this path should be continued or not.

Often, other window objects, such as the input field prompt - are also supposed to be shown or hidden. For these objects, the VOLATILE flag should be set with the same identifier, which here marks a group of logically connected window objects.  

In case a window object refers to a 'normal' data member of a model object, the VOLATILE flag has no effect.