Option 3; XML namespace dispatch


Content-Type: application/compound+xml
<html:body>
  <svg:svg ... />

Con: no support for XML documents like the XSLT stylesheet example

Con: security problems (due to dispatch from intrinsic data

Con: cost of a new media type

Pro: simple, intuitive for common formats

Pro; what some (Mozilla/SVG, Justsystem) are already doing.