W3C home > Mailing lists > Public > public-html@w3.org > January 2010

Re: Decentralised extensibility idea (ISSUE-41)

From: Philip Jägenstedt <philipj@opera.com>
Date: Fri, 15 Jan 2010 10:06:19 +0100
To: "Toby Inkster" <tai@g5n.co.uk>, "public-html@w3.org" <public-html@w3.org>
Message-ID: <op.u6kgwtztsr6mfa@worf>
On Fri, 15 Jan 2010 00:30:21 +0100, Toby Inkster <tai@g5n.co.uk> wrote:

> This is a sketch of a proposal for decentralised extensibility (DE) in
> HTML5. If there is interest in it, I'll be happy to write it up as a
> change proposal, but I'd like to see what people think first.

I like the overall goal, because it is exactly like microdata. Comments  

> The class attribute has traditionally been used mostly by authors for
> their own purposes. That doesn't need to conflict with this solution, as
> I will later indicate a mechanism for documents to specify which
> otherspec(s) they are making use of.

Overloading the class attribute (like microformats) isn't a very good  
idea, it *will* clash with existing markup. The world doesn't end, but  
it's best to avoid, and in fact easy to avoid.

> So, how should one add custom attributes to otherspecs. We repurpose the
> data-* attributes:
> 	<span class="Car" data-engine-size="1.8L"
> 		data-colour="blue">Mazda</span>

What if the original markup were  
<tr><td>Mazda</td><td>1.8L</td><td>blue</td></tr> or any other form where  
the data being marked up is visible in the page?

> Currently the data-* attributes are reserved entirely for the author's
> private use. In this proposal, the definition of those attributes would
> be changed to allow otherspecs to assign particular meaning to data-*
> attributes, but only in the case where document authors have explicitly
> indicated which otherspec(s) they're making use of.

I don't think this is a very good idea, as data-* are always hidden and  
not suitable for marking up content that is visible in the page.

> So, my original XML-style <car/> element could be written as:
> 	<span
> 		profile="http://example.com/CarML/html5"
> 		class="Car"
> 		data-engine-size="1.8L"
> 		data-colour="blue">Mazda</span>

<span itemscope itemtype="http://example.com/CarML/html5#Car">
<span hidden itemprop="engine-size">1.8L</span>
<span hidden itemprop="colour">blue</span>

Of course your example and mine would be much better if the engine size  
and color were actually part of the page, e.g.

<tr itemscope itemtype="http://example.com/CarML/html5#Car">
   <td itemprop="manufacturer>Mazda</td>
   <td itemprop="engine-size">1.8L</td>
   <td itemprop="colour">blue</td>

> An optional extra would be a DOM method
> getElementsByClassNameWithProfile(classname, profileuri) which return a
> collection of elements matching the provided class, but only if they
> were within the scope of a particular profile URI.

Microdata: document.getItems("http://example.com/CarML/html5#Car")

As a side note, I'm not sure what kind of page one would find at  
http://example.com/CarML/html5 in your example, but what is possibly  
missing from microdata is some formal way of describing the vocabulary to  
automate validation. I think it's premature to standardize anything  
though, experimentation is necessary.

Philip Jägenstedt
Core Developer
Opera Software
Received on Friday, 15 January 2010 09:07:05 UTC

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