Re: My review of RDFa Core 1.1 (2011-12-15 version)

Just one small comment.


On Jan 26, 2012, at 03:08 , Niklas Lindström wrote:
[skip]
> 
> 
>>> * The last sentence "As a special case, _: is also a valid reference
>>> for one specific bnode." is the only explanation of what "_:" means. I
>>> think it should be elaborated a little upon, making it clear how it
>>> works and why. (Also I was under the impression that it should
>>> generate a unique bnode each time it is used (and not represent the
>>> same bnode across the document), but that does not seem to be the
>>> case?)
>> 
>> 
>> I have no idea at all what to do here.
> 
> Nor do I. I've never used it, I think usage of empty @typeof fulfills
> my potential needs for what I thought it meant, and I don't really get
> why a kind of bnode "singleton" would be useful at all. Can anybody
> explain what it means and is used for?

There is no mystery here. The question is whether (a) '_:' would be disallowed or not and (b) if not, what it would mean. The group decided that there is no reason to explicitly disallow it. I actually proposed back in the RDFa 1.0 days that '_:' would mean something like a 'fresh' BNode at any place of its appearance, but I was voted down, arguing that it was too complex for our authors (which is probably true), meaning that there is one single BNode whose id is '_:'. Ie, it is not 'used' for anything particular, it is simply a syntactic artifact that is not disallowed.

Ivan

P.S. As a historical value...

My possible usage for '_:' as a 'fresh' BNode was the equivalent of [] in Turtle. Ie,

<div rel="something">
  <div about="_:"> things here </div>
  <div about="_:"> other things here </div>
</div>

would yield

<> something [ things here ], [ other things here ] .

Ie, the author would not forced to come up with explicit bnode ids



----
Ivan Herman, W3C Semantic Web Activity Lead
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