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Re: Character Entities: An XML Core WG View

• To: richard@c...
• Subject: Re: Character Entities: An XML Core WG View
• From: David Carlisle <davidc@n...>
• Date: Tue, 5 Nov 2002 13:56:54 GMT
• Cc: xml-dev@l...
• In-reply-to: <200211051337.NAA09409@m...> (message fromRichard Tobin on Tue, 5 Nov 2002 13:37:24 GMT)
• References: <200211051337.NAA09409@m...>

> Well, I did say "for experimentation".  It could then be standardised
> using the usual &-syntax.

The trouble is I'm not sure that the experiment would provide any useful
feedback.

Given an implementation of some macro expansion mechanism then basically
macros get expanded and so are invisble to the rest of the system, so
whatever macro/entity you come up with, everything works the same way.

However different design choices have radically different behaviour if
the document is processed by a system that doesn't know of the
mechanism or can't find the macro definitions. It's really the behaviour
in these error situations that distinguishes the different design
possibilities.

<foo>\gamma</foo> on a processor that doesn't know this is today's
entity syntax will see that as element content of 6 characters \ g a m m a
In particular the system would provide no warning that anything had been
misunderstood.

whereas <foo>&gamma;</foo> will be seen as a well formed or validity
error depending on what's in the <!DOCTYPE. So experiences gained by
experimenting with \gamma won't really give a good indication of
the user experience if the syntax was switched to &gamma;

In practice I'd like to just use a standard SGML or XMl catalog system
to default a DTD containing entity declarations on to well formed
documents that don't have a doctype but do have entity references,
Apart from this dtd defaulting everything else could proceed as before
and it would not really disrupt my current XML processing practices in
the way that inserting a completely different macro expansion step would
do (and does).

Of course if I use an SGML system, that works now, I can have
<math>
<mo>&gamma;</mo>
</math>
and sp will tell me it's valid if I default the mathml dtd on to
documents with top level element math.  Basically the "experiment" that
I want to do is to be able to say that is pukka XML and the fragment
that I actually pass around is well formed XML.

David

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