[whatwg] [html5] tags, elements and generated DOM

Lachlan Hunt lachlan.hunt at lachy.id.au
Thu Apr 7 23:23:31 PDT 2005

Henri Sivonen wrote:
> On Apr 7, 2005, at 09:58, Lachlan Hunt wrote:
>> There's no reason why a full conformance checker couldn't be based on 
>> OpenSP.
> It would be prudent not to use OpenSP in order to avoid accidentally 
> allowing SGMLisms that are alien to real-world tag soup.

If I ever get around to writing any form of conformance checker, true 
SGML validation (most likely using OpenSP) or XML validation (probably 
using Xerces or other XML parser) is at the top of my list.

Personally, I probably wouldn't make use of a full conformance checker 
too often during my normal publishing process, as I understand semantic 
documents and most likely wouldn't end up writing non-conformant 
documents in that regard anyway.  However, I do make mistakes and forget 
to close elements, misspell attributes and tag-names or whatever, in 
which case an SGML validator catches most of those mistakes for me. 
Yes, I know there are some things like conditionally required attributes 
that cannot be expressed by a DTD, but that doesn't make _true SGML or 
XML_ validation any less of a *very useful conformance tool*.

>> Infact, it would probably be a good idea for them to do so, since then 
>> they'll also be real validators too, which is part of the conformance 
>> requirements.
> I don't think SGML validation is part of What WG conformance 
> requirements.

Considering it seems to be part of the conformance criteria,

| Conformance checkers *must* verify that a document conforms to the
| applicable conformance criteria described in this specification...
| The term "validation" specifically refers to a subset of conformance
| checking...
| 1. Criteria that can be expressed in a DTD.

validation is a critical part of conformance checking.

> I thought Hixie has specifically said he doesn't bother with DTDs.

Just because his authoring practices may not involve their use, doesn't 
mean many other authors don't make use of them.

As real usecase for DTD validation, consider this.  There are increasing 
calls for CMSs to produce strictly conformant markup.  There have been 
many complaints that such conformance is not enforced, which results in 
many invalid and non-conformant websites.  Users should not be required 
to check all of these conformance criteria manually before submitting 
content through a CMS, as experience shows that simply doesn't happen.

If CMSs are ever going to enforce strinctly conformant code, then DTD 
validation will be a core component of that process.  Why re-invent the 
wheel when it comes to that, when a perfectly suitable and proven method 
already exists?  Experience has shown, with all the lints available, 
that validation/conformance checking without a DTD is often incorrect, 
which makes them very useless conformance tools.

This is why HTML must remain an application of SGML, the XHTML version 
*must* be a *valid* application of XML, and why DTDs are so important. 
The only thing we are waiting for in this field is CMSs that actually do 
enforce conformance, which we won't have a chance with if DTDs (or 
Schemas for XML) are not retained.

Lachlan Hunt
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