W3C home > Mailing lists > Public > www-validator@w3.org > August 2004

Re: suggest validator prefer URI to FPI

From: Dominique HazaŽl-Massieux <dom@w3.org>
Date: Tue, 17 Aug 2004 11:03:03 +0200
To: Bjoern Hoehrmann <derhoermi@gmx.net>
Cc: www-validator@w3.org
Message-Id: <1092733383.4811.22.camel@stratustier>
Le ven 06/08/2004 ŗ 05:26, Bjoern Hoehrmann a ťcrit :
> >I think DanC's point was that since URIs are preferred to FPIs in the
> >Web Architecture,
> They are not as far as I can tell.

The WebArch document has
"There are substantial benefits to participating in the existing network
of URIs ... there are substantial costs to creating a new identification
system that has the same properties as URIs."

While it doesn't speak about FPI as such, and while FPI have been
created long before URIs have been, I think it's fair to say that
reading this section of the WebArch documents, one should prefer the
URIs to the FPI as an identification system; for sake of clarity, I'm
really speaking about the identification systems, not the particular
bits of syntax in XML/SGML where FPI and URIs (as System Id) can

>  If they are, the proper place to
> discuss this would be the XML Core Working Group so they can write
> this important bit of information into the XML 1.0 Recommendation.
> Until that happens, SIs are not preferred to FPIs in any relevant way.

Note that indeed, SIs are not preferred to FPIs according to any
relevant spec; I think the point is "if you develop something with the
Web in mind, try and use URIs in preference to another identification
system". Since the Validator is definitely developed with the Web in
mind, DanC was suggesting to investigate the benefits one could get of
using URIs.

> That depends on how it would be determined whether FPI and SI "differ".
> For example, my document is
>   <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN"
>     "/dtd/xhtml11">
> [...]
> It's like that so I can ssh to the server and run `xmlvalid` on the
> entire file tree without need for external resources or a catalog
> system. What would the Validator do exactly?

The Validator would notice that the System ID URI is not the one it
associates by default to the FPI; depending on the feasibility of the
different approaches, it could:
1. simply emit a warning saying that it doesn't know whether the System
ID matches the FPI, and lists the "officials" System IDs bound to the
2. download and cache the DTD, and "compare" it to the official DTD -
I've no idea how feasible it is to compare DTDs though - emitting an
error if they don't match, and validating using the downloaded DTD
3. download and cache the DTD, validate the document with the downloaded
DTD and emit the warning as in 1.

Given that custom System IDs probably aren't that frequent anyway, I
think at least starting with 1 could be a benefit for the user.

>  If /dtd/xhtml11 is
> http://www.w3.org/TR/2001/REC-xhtml11-20010531/DTD/xhtml11-flat.dtd
> it would seem inappropriate to fetch additional 150KB document from
> my server any time someone validates one of my documents

(Note that it wouldn't need to be each time someonce validates the
document; that's what caching is for)

> , as it would
> seem inappropriate to suggest that there is anything wrong with
> my document.

It depends on how wrong this is suggested to be; I don't think a simple
warning that the System ID is different would be inappropriate.

Dominique HazaŽl-Massieux - http://www.w3.org/People/Dom/

Received on Tuesday, 17 August 2004 09:06:22 UTC

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