"uriref()" XPath function?

I notice there's an "idref()" XPath function which returns nodes which
reference a specified id - however the document I'm processing
references ids with URIs, e.g. <a href="#foo"/> references id "foo"

Is there something like a "uriref()" function? which given an id,
returns nodes which reference it with URIs?

According to RFC 3986 section 4.4,
http://tools.ietf.org/html/rfc3986#section-4.4

 - nodes where,

1. the URI, resolved against the base URI, aside from its fragment
component (if any), is identical to the base URI
2. the fragment component is identical to a specified id