[whatwg] [WF2] Web Forms 2.0: Repetition and type ID

Ian Hickson ian at hixie.ch
Sun Jul 3 06:11:30 PDT 2005

On Fri, 1 Jul 2005, fantasai wrote:
> While we're on the topic.. what sorts of things would HTML5 conformance 
> checkers have to do that is impossible to express in schema languages? 
> (Aside from checking semantic correctness, of course. I hope you aren't 
> expecting that from a piece of software.)


Examples, assuming we are just talking about the XML version of HTML5 and 
not the "HTML" version (for lack of a better name):
 * checking the MIME type of the file
 * there must not be more than one <dfn> per term
 * some of the more exotic content models, e.g. <ins>, <del>, the 
   distinction between inline-level containers and block-level containers
 * checking conformance of <meta> elements (requires parsing a profile)

...and of course:

 * IDs may contain any characters, not just those allowed in XML IDs.

There are also things which will probably require warnings from 
conformance checkers, e.g. violations of SHOULD requirements, including 
e.g. making sure the appropriate <hx> header is used in sections.

> > I don't understand what you mean when you say authoring tools would 
> > have problems; why would they?
> Generic XML editors like XXE have support for using a schema to guide 
> the editing process, but have no knowledge specific to a given language 
> like XHTML. These tools, and other generic XML tools, will not be able 
> to recognize the IDness of the 'id' attribute if it's not possible to 
> express this in a schema.

As mentioned, that will be the least of their problems.

> > > I don't care what the syntax is (I suggest :-replaceable-: for lack of
> > > anything better), and it doesn't have to apply to other attributes where
> > > [replaceable] is more natural.
> > 
> > Ok, I allowed two other characters to be used in the place of [] as well.
> Apologies for second-guessing you, but I don't believe that U+2045 or
> U+2046 are valid NameChars either.
>   http://www.w3.org/TR/2000/WD-xml-2e-20000814#NT-NameChar

Sigh. Can someone please explain why there is a completely ridiculous 
restriction on the values of IDs???

Next I was going to use U+02AD .. U+02AC, but since these are new 
characters, they're only in XML 1.1, not XML 1.0. I presume _that_ is a 
problem for everyone as well?

I've changed them to use U+02D1 and U+00B7 instead, which looks stupid but 
will hopefully make everyone happy. (I didn't want to use two characters 
because that can make parsing this a whole lot more complex, and I didn't 
want to use "-", "_", or "." because they are way too common and so we'd 
be getting unintentional replacements left right and centre, and I didn't 
want to use ":" at all because of the way that character has special 
meaning for namespaces these days.)

Ian Hickson               U+1047E                )\._.,--....,'``.    fL
http://ln.hixie.ch/       U+263A                /,   _.. \   _\  ;`._ ,.
Things that are impossible just take longer.   `._.-(,_..'--(,_..'`-.;.'

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