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

Re: The harm that can come if the W3C supports publication of competing specs

From: Philip Jägenstedt <philipj@opera.com>
Date: Tue, 19 Jan 2010 02:35:06 +0100
To: "Ian Hickson" <ian@hixie.ch>
Cc: "Toby Inkster" <tai@g5n.co.uk>, "HTMLWG WG" <public-html@w3.org>
Message-ID: <op.u6raoshdsr6mfa@worf>
On Tue, 19 Jan 2010 02:14:41 +0100, Ian Hickson <ian@hixie.ch> wrote:

> On Mon, 18 Jan 2010, Philip Jägenstedt wrote:
>> On Sun, 17 Jan 2010 20:47:29 +0100, Toby Inkster <tai@g5n.co.uk> wrote:
>> > Cyclical references amongst blank nodes cannot be represented in
>> > Microdata. In Turtle an example might be:
>> >
>> > 	@prefix foaf: <http://xmlns.com/foaf/0.1/> .
>> > 	_:bob foaf:knows _:jon .
>> > 	_:jon foaf:knows _:bob .
>> >
>> > In RDFa it can be expressed quite simply:
>> >
>> > 	<p xmlns:knows="http://xmlns.com/foaf/0.1/knows"
>> > 	   about="_:jon" rel="knows:" rev="knows:" resource="_:bob">
>> > 	  Jon and Bob know each other.
>> > 	</p>
>> >
>> > To express the same semantics in Microdata would require assigning a  
>> URI
>> > to at least one of the people. Certainly it's possible for a script to
>> > assign a URI on the fly, but committing to maintaining the meaning of
>> > that URI long-term is harder, which is why blank nodes are so  
>> frequently
>> > used in RDF.
>> >
>> > I believe, this could be addressed by allowing @itemid to contain a
>> > blank node name, and providing a way for @itemprop to specify a blank
>> > node as its value.
>>
>> Right, if there's an actual need then it's easy to hardwire the _:foo
>> syntax to create blank nodes in the RDF extraction algorithm. Currently
>> the algorithm ignores item types which aren't absolute URIs. Is _:foo an
>> absoute URI, or is it not a URI at all?
>
> Looped references are one of the features that were explicitly deferred  
> to
> the next version, because there simply weren't use cases that needed it.  
> I
> designed the mechanism that one would use to do it back when first  
> writing
> the Microdata section, I just didn't include it.

What mechanism did you have in mind and does it still hold, so that it's  
possible to add in the future should it actually be needed? I have no  
particular desire for it, but I'd like to know what "plan B" is and that  
it doesn't break things.

-- 
Philip Jägenstedt
Core Developer
Opera Software
Received on Tuesday, 19 January 2010 01:35:25 GMT

This archive was generated by hypermail 2.2.0+W3C-0.50 : Wednesday, 9 May 2012 00:16:59 GMT