W3C home > Mailing lists > Public > public-rdf-in-xhtml-tf@w3.org > July 2007

Re: moving forward!

From: Ivan Herman <ivan@w3.org>
Date: Thu, 26 Jul 2007 11:09:58 +0200
Message-ID: <46A864E6.2060600@w3.org>
To: Niklas Lindström <lindstream@gmail.com>
Cc: Ben Adida <ben@adida.net>, RDFa <public-rdf-in-xhtml-tf@w3.org>


Niklas Lindström wrote:
> 
> == Striping ==
> 
> A. I want to interpret the rules given
> (<http://lists.w3.org/Archives/Public/public-rdf-in-xhtml-tf/2007Jul/0158.html>)
> 
> to determine subject for nested content (i.e. corresponding RDF
> identity) in a generalised way as:
> 
>    - If a relation (with @rel) to a resource is given, that object is
> used as subject for nested content.
>    - If that object is not explicit, a bnode is generated and used.
>    - Unless the above, use the subject given in the element (by
> @about, perhaps by @id - see [C] below).
>    - If nothing of this applies, keep the current (inherited) subject.
> 
> Does this make sense?
> 

At first reading it does to me except for @instanceof (see below)... and
I think it is in line with Ben's rules.


> B. Furthermore, I'm uncertain about what the resulting state should be
> when @rev is used? Consider:
> 
>    <div about="#something" rev="dct:hasPart" resource="">
> 
> which AFAIK yields:
> 
>    <> dct:hasPart <#something> .
> 
> But what will the subject be for nested content? <#something> or <>?
> Compare with this:
> 

I think Ben's rules are clear on that: subject of nested content will be <>:

[[[
the subject of an element's *content* is the element's corresponding
RDF identity when @rel, @rev, @href, @resource, or @instanceof appears.
Otherwise, it's @about resolution.
]]]

And the RDF Identity is the value of @resource.


>    <div rel="dct:hasPart" resource="something">
> 
> yielding the same triple as above, and according to the rules clearly
> having <#something> as the "nested subject". This becomes even
> trickier for me if both @rel and @rev is present, or if @resource is
> absent.
> 

I do not really see a problem on the algorithmic level. @rel or @rev do
not affect that choice of the RDF Identity...

On a user level... well, I always considered @rev as a probably
necessary thing but which is/should be used in somewhat exceptional
circumstances anyway...

> C. Finally (perhaps digressing). If @id is to be used at all, I wonder
> if @about should not have precedence over this (as opposed to the
> proposed order of the rules referred to above). This to enable
> explicit prevention of non-semantic @id:s to have significance. Still,
> I suppose this is the subject for another discussion.
> 
> 
> == The rdf:type shorthand ==
> 
> D. Regarding rdf:type, will this shorthand be a syntactic one based
> upon the (above) subject striping rules? As opposed to another
> resolution technique possibly directly affecting the striping
> algorithm?
> 
> Assuming the former, is the rdf:type attribute (say @instanceof) a
> plain shorthand for a child element with @rel="rdf:type" and a
> @href/@resource? This must probably be the case, since if it is a
> shorthand for putting the @rel etc in the same element, that would
> make, by following the current idea of striping, the *type* the nested
> subject.
> 

Again, I think Ben's rules are clear on that:

[[[
the element's corresponding RDF identity is the subject of an rdf:type
triple when instanceof appears.
]]]

ie, it is _not_ a purely syntactic sugar, but has its own rule of usage.
And I have the impression that this fits pretty well our different use
cases... Anybody is of course allowed to use a rel="rdf:type" and fall
back on the general mechanism (if wished).


> Though, if @instanceof is a shorthand for a nested element doing the
> typing, its presence would not make the element where it appears mean
> anything for RDFa itself, e.g. generate any bnode (or eventual special
> @id treatment), which *may* be desired..
> 
> That would also make @instanceof appearing alone strange (typing an
> ancestor?). Because of this, perhaps a condition for the rdf:type
> shorthand should be that a "corresponding RDF identity" resolution
> must occur for the same element it appears in (otherwise either
> yielding nothing or even be an error).
> 
> Or else it speaks for the latter case - a special rule both depending
> on and affecting striping.
> 
> E. Finally, for future thought, does it seem reasonable that when this
> attribute appears at the root element of a document (or even head in
> XHTML), its xml:base (explicit or implicit) will be the subject of the
> rdf:type statement? I suppose so (and that this works for either case
> here).


Hm, that is interesting, but regardless of @xml:base.


<html instanceof="foo:bar">

would mean, according to Ben's rule that a blank node is created:

_:bb rdf:type foo:bar

and, from then on, _all_ RDFa statements are relevant to _:bb, ie, this
sets the new context. Unless explicitly referred to, <> will never be
valid. I am not sure that is bad, but just shows a side-effect of our
rules. But I do not see how @xml:base would have an influence on anything...

Ivan

> 
> 
> I sincerely hope these questions can be of relevance.
> 
> Best regards,
> Niklas
> 
> 
> 
> 
> On 7/23/07, Ben Adida <ben@adida.net> wrote:
>>
>>
>> Hi all,
>>
>> I suspect we're all hitting a little bit of spec fatigue. That said, we
>> need to push through! We have one relatively important issue to cover
>> (how striping really works), and a handful of smaller issues.
>>
>> So, *everyone* should take an action to think about and contribute
>> thoughts on this list to the following issues, some time before Thursday.
>>
>> 1) Striping. @rel everywhere is hugely useful, but it does complicate
>> things. Mark's latest description of what we should do:
>>
>> http://lists.w3.org/Archives/Public/public-rdf-in-xhtml-tf/2007Jul/0145.html
>>
>>
>> and my proposed tweak with complete rules:
>>
>> http://lists.w3.org/Archives/Public/public-rdf-in-xhtml-tf/2007Jul/0158.html
>>
>>
>>
>> 2) the attribute name we should pick for rdf:type. It seems the only two
>> real contenders so far are @instanceof, and @kind. I recently proposed
>> @resourcetype, though haven't heard any feedback.
>>
>> Time to submit last suggestions including your top preference!
>>
>>
>> 3) RDF containers and collections
>>
>> Last proposal and discussion:
>> http://lists.w3.org/Archives/Public/public-rdf-in-xhtml-tf/2007Jul/0122.html
>>
>> http://lists.w3.org/Archives/Public/public-rdf-in-xhtml-tf/2007Jul/0131.html
>>
>> http://lists.w3.org/Archives/Public/public-rdf-in-xhtml-tf/2007Jul/0139.html
>>
>>
>>
>> 4) xml:lang
>>
>> We mentioned some solutions to this in the default datatype issue:
>>
>> http://lists.w3.org/Archives/Public/public-rdf-in-xhtml-tf/2007Jun/0039
>>
>> are we okay with the conclusion of this with respect to xml:lang?
>>
>>
>> 5) The @src attribute on IMG. I think this one is pretty much done, but
>> we need to resolve it:
>>
>> <img about="#me" rel="foaf:image" src="ben.jpg"
>> instanceof="foaf:Image" />
>>
>> yields
>>
>> <#me> foaf:image <ben.jpg> .
>> <ben.jpg> rdf:type foaf:Image .
>>
>> Any remaining issues on this for XHTML1.1+RDFa? I don't think so, but
>> speak up if you do!
>>
>>
>>
>> -Ben
>>
>>
> 

-- 

Ivan Herman, W3C Semantic Web Activity Lead
Home: http://www.w3.org/People/Ivan/
PGP Key: http://www.ivan-herman.net/pgpkey.html
FOAF: http://www.ivan-herman.net/foaf.rdf



Received on Thursday, 26 July 2007 09:09:58 GMT

This archive was generated by hypermail 2.2.0+W3C-0.50 : Tuesday, 8 January 2008 14:15:08 GMT