attr() construct in generated content and namespaces

How exactly does the attr() construct work in the presence of namespaced 
attributes?  For example, what is the expected rendering of:

<div xmlns:xlink="whatever"
      xmlns:myNS="somethingElse"
      xlink:type="convoluted"
      myNS:type="confusing"
      type="confounding" />

styled with:

div::before { content: attr(type) }

?

Or in other words, what is it that goes between the parentheses of 
attr()?  The CSS2(.1) spec if pretty vague on this, saying that it's a 
"string that is not parsed by the CSS parser", but CSS2 is generally not 
namespace-aware...

-Boris