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Re: draft proposal for catalog resolution

From: Michael Sperberg-McQueen <U35395@UICVM.UIC.EDU>
Date: Tue, 01 Apr 97 06:42:47 CST
Message-Id: <199704011302.IAA22385@www10.w3.org>
To: W3C SGML Working Group <w3c-sgml-wg@w3.org>
On Tue, 1 Apr 1997 04:17:26 -0500 Martin Bryan said:
>The problem I have is the one you seem to recognize yourself. If
>someone adds a keyword to a catalog because he has facilities for
>interpreting it, how can he be sure that someone without those
>facilities can use it?  ...

By 'use it' do you mean 'use the new keyword', or
'use the catalog'?

The draft wording says keywords other than public may but need
not be supported by XML processors.  I don't know what part of this
is unclear.   If you add a FREEMJET keyword to the SGML Open
Catalog, the XML-lang spec does not promise you that my XML
processor will be able to 'use' it in the sense of correctly
doing whatever it is you want processors to do with a FREEMJET
entry.  If you want that promise, you need to get it on the basis
of other agreements which are, perforce, outside the scope of
the XML-lang spec.

>                   ... Is it a requirement that the addition of
>keywords to a catalog means that the catalog can only be used on
>sites that support that keyword?

No, it is not.  The draft wording defines a catalog file (which ought
probably to be called a catalog entry file, in line with Paul Grosso's
more careful terminology) as containing keywords other than PUBLIC.
That means an XML processor must be able to read past them, whether it
chooses to support them or not.  So if you add a FREEMJET keyword to the
SGML Open Catalog, the XML-lang spec does promise you that my XML
processor will be able to read past the FREEMJET entries, and therefore
that even processors which don't support FREEMJET (or, for that matter,
CATALOG, ENTITY, DELEGATE, or any of the other keywords defined by the
full SGML Open 9401 spec) will be able to use the PUBLIC entries in your
catalog file (as well as any other entry types the processor supports).

If there is another way to interpret the draft wording (e.g. as meaning
that an XML processor is required to handle the FREEMJET keyword, or
that an XML processor is allowed to signal an error on the CATALOG
keyword), I would be grateful for an explanation of that other
interpretation.  At the moment, the draft still seems unambiguous to me.

-C. M. Sperberg-McQueen
Received on Tuesday, 1 April 1997 08:02:27 EST

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