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Re: Named character entities

From: Ian Hickson <ian@hixie.ch>
Date: Sun, 18 May 2003 18:57:55 -0700 (PDT)
To: John Lewis <lewi0371@mrs.umn.edu>
Cc: "www-html@w3.org" <www-html@w3.org>
Message-ID: <Pine.LNX.4.50.0305181852170.22822-100000@dhalsim.dreamhost.com>

On Sun, 18 May 2003, John Lewis wrote:
> You seem to be saying that XHTML can't provide additional restrictions
> (beyond XML) and still be XML. I don't understand where you're getting
> this from.

More to the point, XHTML can't make restrictions on XML parsers beyond
those of XML. This has to be the case so that arbitrary XML parsers can be
re-used in XHTML environments, otherwise XHTML processors must have
specialised XML parsers.

XHTML UAs are expected to be built on top of generic XML parsers. For
example, Mozilla is built on Expat. Mozilla's XHTML support is totally
distinct from its parser -- it isn't until someone later in the process
that the XHTML-specific code hooks in. (In the case of Mozilla and XHTML1,
we used a cut down version of the DTD and use that if an appropriate
DOCTYPE is specified -- but if the XHTML is included in an XML document
using namespaces and no DOCTYPE, as is expected to be relatively common,
entities will not be available, and rightly so.)

In the case of entities, XML says that non-validating parsers need not
recognise anything outside of the five pre-defined entities. Thus, an
arbitary non-validating XML parser will probably not recognise the XHTML
entities. By the time the XHTML-specific part of the UA gets involved, it
is likely that the entities are long lost.

Ian Hickson                                      )\._.,--....,'``.    fL
"meow"                                          /,   _.. \   _\  ;`._ ,.
http://index.hixie.ch/                         `._.-(,_..'--(,_..'`-.;.'
Received on Sunday, 18 May 2003 21:56:45 UTC

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