Linking: ID + SVGViewSpec?

Hi all

I noticed while testing an idea the other day that the fragment identifiers
spec is now a little deficient, in that it assumes the other SVG is in an
external document.

Given that pages containing multiple SVG elements are becoming very
common.  It might be nice to be able to reference another SVG within the
document *and* supply an SVGViewSpec.

An example use case could be:

<svg id="main-image" width="1000" height="1000" viewBox="0 0 1000 1000">
   ...
</svg>

<svg id="zoomed-detail">
  <use xlink:href="#main_image#svgView(viewBox(100,200,20,20))" width="100"
height="100"/>
</svg>

Thoughts?  Would it be useful to extend fragment identiers in some way in
order to allow an ID plus an SVGViewSpec etc?

Paul