• From: Eric Bohlman <ebohlman@n...>
• To: Pierre Morel <pierre-morel@s...>
• Date: Mon, 27 Sep 1999 18:01:00 -0700 (PDT)

On Mon, 27 Sep 1999, Pierre Morel wrote:

> Why the XML specs declare two production rules with identical structure ?
> 
> [30]  extSubset ::=  TextDecl? extSubsetDecl
> 
> and
> 
> [79]  extPE ::=  TextDecl? extSubsetDecl
> 
> I don't understand very well the purpose of having two identical production
> rules.

Neither extSubset nor extPE are used as non-terminals in any other
productions; rather they're referred to in the text in statement of the
form "foo is well-formed if it matches the production labelled bar."  It's
just a coincidence of implementation that external subsets and external
parameter entities have the same syntax, and the redundancy makes human
communication easier.  Tim Bray could probably tell us if the redundancy
were the result of an earlier draft specifying different syntaxes for the
two cases.



xml-dev: A list for W3C XML Developers. To post, mailto:xml-dev@i...
Archived as: http://www.lists.ic.ac.uk/hypermail/xml-dev/ and on CD-ROM/ISBN 981-02-3594-1
To (un)subscribe, mailto:majordomo@i... the following message;
(un)subscribe xml-dev
To subscribe to the digests, mailto:majordomo@i... the following message;
subscribe xml-dev-digest
List coordinator, Henry Rzepa (mailto:rzepa@i...)

• References:
  • Identical production rules
    • From: "Pierre Morel" <pierre-morel@s...>

• Prev by Date: Re: RFC: Attributes and XML-RPC
• Next by Date: Re: groves dissent
• Previous by thread: Identical production rules
• Next by thread: Check this
• Index(es):
  • Date
  • Thread