From https://lists.oasis-open.org/archives/office-comment/200903/msg00155.html :
For extensions of SVG, ODF should follow the guidelines detailed in
the SVG specification:
http://www.w3.org/TR/SVGTiny12/extend.html#ForeignNamespacesPrivateData
Where ODF extends on svg semantics and names, we should adhere to
their reuse policy.