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Re: XML catalog draft



paul@arbortext.com (Paul Grosso) writes:
>> From: murray@spyglass.com (Murray Altheim)
>>
>>     <!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.0//EN"
>>                           "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
statement:

>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

```````````````````````````````````````````````````````````````````````````````
    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."