The question that remains in my mind is the graphical effect. If you have
three children aps; foo:one, foo:two, and foo:three, and you change the
style of foo:two, do all three have to be re-generated in the graphical
display? Is there a difference depending on the choice of whether foo:one
or foo:three is first child?
That would depend on the style you change, if you made foo:two invisible, you
would need to regenerate the entire graphic,
if you only increased the line width, you might be able to only regenerate
foo:two and all graphical elements that
follow foo:two in sequential order of the cgm file. It would make no
difference if you defined foo:one or foo:three as first
child you would still need to process the graphic elements in the order they
are presented in the CGM.