- From: Richard Tobin <richard@inf.ed.ac.uk>
- Date: Thu, 8 Mar 2007 15:56:00 +0000 (GMT)
- To: "Grosso, Paul" <pgrosso@ptc.com>, <public-xml-core-wg@w3.org>
> What is not clear is that XML specifically forbids bare surrogates
> (ie, half of a surrogate pair). This came up in recent SVG WG
> discussions. Is the XML parser required to reject an xml document
> containing a bare surrogate? Would that be a well formedness error, or
> some other sort of error?
I'm not sure what the question means. Here are two possibilities:
(a) Does XML allow unpaired surrogates in a UTF-16 (etc) document?
No, unpaired surrogates are not legal in UTF-16 ("ill-formed"
according to D35 in section 3.9 of Unicode 4.0), so by 4.3.3
it is a fatal error because it is "determined ... to be in a
certain encoding and contains byte sequences that are not legal
in that encoding". Presumably the wording in that section about
irregular UTF-8 code unit sequences is no longer required, since
recent Unicode make it clear that these are ill-formed.
(b) Does XML allow characters whose code point is that of a surrogate?
No, because it would violate production 2.
-- Richard
Received on Thursday, 8 March 2007 15:56:17 UTC