This function
indicates that all access to the VariantVariant attribute of the current
FrameFrame should should be forwarded to some other nominated Frame in
the FrameSetFrameSet. For instance, if a value is set subsequently for the
Variant attribute of the current Frame, the current Frame will be left
unchanged and the setting is instead applied to the nominated Frame.
Likewise, if the value of the Variant attribute is requested, the
value returned is the value stored for the nominated Frame rather
than the current Frame itself.
This provides a mechanism for propagating the effects of variant
Mappings around a FrameSet. If a new Frame is added to a FrameSet
by connecting it to an pre-existing Frame that has two or more variant
Mappings, then it may be appropriate to set the new Frame so that it
mirrors the variants Mappings of the pre-existing Frame. If this is
done, then it will be possible to select a specific variant MappingMapping
using either the pre-existing Frame or the new Frame.