EntityID (and other URI) comparisons

Somebody asked me on another list recently where the normative requirement
that entityIDs be compared case-sensitively was, and I gave the same answer
I have in the past, that it's from the section on string comparisons in core
that says all strings "or types derived from it" use binary comparison.

Unfortunately, anyURI is not derived from string, which I guess was an
oversight.

I guess the best way to handle this would be to add similar text to the
section in core on URIs, and maybe say "any URIs used as identifiers are
compared using binary comparison".

I'd be inclined to make it a MUST, actually, because it's pretty clear we
intended the string section to cover this. I'm not aware of anybody
comparing URIs used as entityIDs or attribute names or name formats, etc. in
any other way.

-- Scott