W3C home > Mailing lists > Public > w3c-sgml-wg@w3.org > February 1997

Re: XML catalog draft

From: Murray Altheim <murray@spyglass.com>
Date: Tue, 11 Feb 1997 16:42:57 -0400
Message-Id: <v02140b00af2687c07741@[]>
To: paul@arbortext.com (Paul Grosso)
Cc: w3c-sgml-wg@w3.org
paul@arbortext.com (Paul Grosso) writes:
>> From: murray@spyglass.com (Murray Altheim)
>>                           "http://www.cm.spyglass.com/dtd/html.dtd">
>> This announces to the world that the document conforms to HTML 2.0, but
>> tells the processor that a local copy of 'html.dtd' will provide the
>> resource without resorting to a PUBLIC catalog lookup. IOW, why bother
>> resolving the reference if the document seems to know where to look. Then,
>> if the SYSTEM fails, resort to the more generalized process of a catalog
>> lookup using PUBLIC.
>But suppose I have a local copy of the HTML 2.0 DTD (and who wouldn't),
>so my local system default catalog has:
>  PUBLIC "-//IETF//DTD HTML 2.0//EN" "/home/dtds/html.dtd"
>If you prefer SYSTEM, then there is no way to find the local copy in
>favor of the spyglass one (unless the latter fails).

I didn't mean to imply a behavior at all. What that DOCTYPE says is that
there are both SYSTEM and PUBLIC available, not which one is given
preference. I'm not advocating constraining UA behaviour. Your converse

>In other words, in answer to "why bother resolving the reference if the
>document seems to know where to look" I'd answer "why bother to have a
>public id that allows the all-important indirection if you going to
>ignore it in most cases."

is true iff the UA is set to prioritize SYSTEM over PUBLIC. Please note
that I was not stating that converse, I was replying to David's statement:

dgd@cs.bu.edu (David Durand) Tue, 11 Feb 1997 13:57:52 -0500 writes:
>Since PUBLIC is likely to be a point of user-tailorability, it should be
>looked at first -- implementations that don't implement PUBLIC resolution
>will simply ignore the PUBLIC, thus causing it to "fail". I can't think of
>a case where someone who _has_ working public resolution, would prefer to
>use the system ID -- andif they did, it seems they could always ensure that
>any given public ID (or all) would fail to resolve.

by trying to state that a general, simplistic rule is not possible.

>Public ids aren't just a fallback for broken URLs, they are a very
>important way to manage indirection of resource name resolution.

Agreed. I'm in agreement with David's last summary on the subject:
>Depending on how the software caches data, the optimal strategy may be
>very complex. I'm now thinking we should not get in the way of processing
>agents defining their own strategies _however_ they want to.


    Murray Altheim, Program Manager
    Spyglass, Inc., Cambridge, Massachusetts
    email: <mailto:murray@spyglass.com>
    http:  <http://www.cm.spyglass.com/murray/murray.html>
           "Give a monkey the tools and he'll eventually build a typewriter."
Received on Tuesday, 11 February 1997 16:37:45 UTC

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