update on reference element doesn't reflected by the referencing element
for example I have rect element with fill attr point to gradientElement, if I
update the gradient element
property/child the update doesn't reflected by GVT.

work around for batik user (not developer)
when update the reference element, update also the referencing element by
setting/update any attribute

according to the batik-users mailing list
"This is a known limitation.  This is _much_ harder than you think
since gradients can reference other gradients etc... In particular it
is difficult to avoid memory leaks (this was supported early on but
was removed because the memory leaks were so bad)."