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Re: RDFa Lite and non-RDFa @rel values

From: Alex Milowski <alex@milowski.com>
Date: Tue, 24 Apr 2012 10:33:47 -0700
Message-ID: <CABp3FN+T=uFxhokZackTAk9yy0YDxC03vZQiH0=8G=mSM-dizA@mail.gmail.com>
To: RDFa WG <public-rdfa-wg@w3.org>
On Tue, Apr 24, 2012 at 9:55 AM, Ivan Herman <ivan@w3.org> wrote:
> It is of course unfortunate that this discussion comes now. The practical problem is that a change of the processing rules as you are proposing means going back to last call and, as for now, would seriously jeopardize the publication of the spec in time. It would also seriously affect the acceptance of rdfa through a delay. I would really like to avoid that, unless there is a real bug somewhere.

I understand the sentiment.  A substantive change would send the
specification back through CR.

That means, the real question comes down to what we expect from this
kind of markup:

   <a vocab="..." href="http://www.w3.org/" rel="nofollow"
property="homepage">W3C's Home Page</a>

Should it be:

   <> <http://www.w3.org/1999/xhtml/vocab#nofollow> <http://www.w3.org/>
   <> <...homepage> "W3C's Home Page"

or

   <> <http://www.w3.org/1999/xhtml/vocab#nofollow> <http://www.w3.org/>
   <> <...homepage> <http://www.w3.org/>

?

Note that you can't get the second set of triples from the same link
(@href value) through some other structure without repeating the link
element somehow.  As such, the second set isn't possible without
changing the specification and that would lead to a new CR period.

Via how Step 6 in section "7.5 Sequence" works, you can get a similar
result by typing the link:

   <a vocab="..." href="http://www.w3.org/" rel="nofollow"
typeof="homepage">W3C's Home Page</a>

which generates:

   <> <http://www.w3.org/1999/xhtml/vocab#nofollow> <http://www.w3.org/>
   <http://www.w3.org/> rdf:type <...homepage>

and the neat thing about that is descendant facets are in relationship
to the @href value as the new subject:

   <a vocab="..." href="http://www.w3.org/" rel="nofollow" typeof="homepage">
   <span property="dc:title">W3C's Home Page</span>
   </a>

   <> <http://www.w3.org/1999/xhtml/vocab#nofollow> <http://www.w3.org/>
   <http://www.w3.org/> rdf:type <...homepage>
   <http://www.w3.org/> dc:title "W3C's Home Page"

Typing links like this has become my new favorite expression.  :)

If this wasn't the CR period, I would suggestion changing how
@property is handled in the presence of @rel/@rev.  That feels like
the right thing to do so that authors aren't surprised by a "simple"
change.

I can live with how things are right now, even though it isn't ideal,
given that I have a rational explanation: The resource identified by
@href is "consumed" by the presence of the @rel, so @property is
interpreted different.  Synopsis: you lose, change your markup if you
want something different.

But, if the right thing to do is to change Step 11, that option should
strongly be considered.  We can't go back and change this after this
becomes a Recommendation.  It would be a breaking change and so we'd
have to live with it going forward.

Maybe a different question is helpful?

How common is it to want to associate the link target with a different
predicate when @rel is present and already generating one predicate?
That is, how common is it to have two predicates associated with one
link target?

-- 
--Alex Milowski
"The excellence of grammar as a guide is proportional to the paucity of the
inflexions, i.e. to the degree of analysis effected by the language
considered."

Bertrand Russell in a footnote of Principles of Mathematics
Received on Tuesday, 24 April 2012 17:34:21 GMT

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