To be equivalent the SVG `<path>` element would probably need to take an idref to something like a `<draw>` element. This is how I would guess the equivalent would be:

    <draw id="my-path">
      <move-to x="10" y="10" />
      <line-to x="90" y="10" />
      <line-to x="90" y="90" />
      <line-to x="10" y="90" />
      <line-to x="10" y="10" />
    </draw>

    <path draw="my-path" />

EDIT: Come to think of it, the above is probably a lot easier to animate using CSS or SMIL. Animating the `d` attribute on `<path>`s is theoretically possible but in practice weird at best or browser inconsistent or simply impossible at worst.

EDIT 2: In D3 it is not uncommon to draw area graphs with a thick border on top. The only way to do this is with two `<path>`s with almost identical `d` attributes. Allowing drawings to be strung together with multiple idrefs could solve that:

    <draw id=line-path><!-- ... --></draw>
    <draw id="area-box-close">
      <line-to x="100" y="100" />
      <line-to x="0" y="100" />
      <end />
    </draw>
    
    <path draw="line-path" class="line" />
    <path draw="line-path area-box-close" class="area" />

Maybe this isn’t such a bad idea after all.