Jukka K. Korpela wrote:
> In future, please quote or paraphrase the message that you are 
> commenting on.

I usually do. Apologies.

> It depends on. There's no law that requires additional rules

Granted. It's rare that there aren't any, in my experience, unless the 
document type is pure structure.


>> Think of
>> these as "higher-level syntax checking"; the application is always
>> going to impose semantic constraints as well.
> 
> What's "higher-level" here?

Higher than the basic XML syntax.

> Anyway, in the issue discussed in this 
> thread, it is the additional _syntactic_ constraints that imply that a 
> certain kind of document is not an HTML document.

That's what I was agreeing with, though apparently I may have phrased it 
badly. The DTD is not always a completely constrained specification of 
"a kind of document". That flexibility may in fact have been deliberate; 
I strongly suspect the intent was that a single DTD could describe 
several documents which share related structures.

> Whether HTML specifications make such a 
> requirement is debatable; the prose in the specs is a mixture of 
> normative-looking prose, comments, hints, wishful thinking, etc.)

http://www.w3.org/TR/1999/REC-html401-19991224/struct/global.html#h-7.1

The complicating factor here is the use of the word "should". The HTML4 
spec predates the W3C's adoption of the normative use of MAY, SHOULD, 
and MUST to mean "optional", "don't violate this without extremely good 
reason", and "required by the spec" respectively. So we need to 
crosscheck that.

XHTML 1.0 does follow that convention, so we can backhandedly check the 
intent by looking at that spec. There, a Strictly Conforming Document 
must (!) have html as its root element, and this is *NOT* flagged as one 
of the differences from HTML4 either in this spec or in the 
compatability guidelines (http://www.w3.org/TR/xhtml1/#guidelines). This 
strongly suggests that the W3C intended that HTML4 docs follow this rule.

I agree, that's a less than ideal way to answer this question, but I can 
tell you that even folks working on the W3C's specs often have to resort 
to that kind of pointer chasing to nail things down.

If you need a fully official answer... I haven't checked; are any of us 
members of the (X)HTML Working Group? If not, I'd suggest dropping a 
quick note to www-html@w... and suggesting that it might be good to 
have an erratum which clarifies whether this "should" was intended to be 
"must" or not. (I checked; there isn't one.)

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() ASCII Ribbon Campaign  | Joe Kesselman
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