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Re: RDFa Lite and non-RDFa @rel values

From: Ivan Herman <ivan@w3.org>
Date: Tue, 24 Apr 2012 18:55:45 +0200
Message-Id: <5BD5A797-D20B-4E8A-9F23-B14A5B684B99@w3.org>
Cc: RDFa WG <public-rdfa-wg@w3.org>
To: Alex Milowski <alex@milowski.com>
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.

Sorry, I am on the road now, and cannot really get into the discussion, I just wanted to share my concern... (this comment is also valid for the rdfa lite conformance issue; I really would try to avoid touching the processing rules)

cheers

Ivan

----
Ivan Herman
+31 641044153

(Written on my mobile. Excuses for brevity and frequent misspellings...)



On 24 Apr 2012, at 16:18, Alex Milowski <alex@milowski.com> wrote:

> On Mon, Apr 23, 2012 at 7:49 PM, Stéphane Corlosquet
> <scorlosquet@gmail.com> wrote:
>> (by RDFa Lite, I really mean the new behavior of the property attribute)
>> 
>> It is common for web developers to add a rel attribute in 'a' elements, e.g.
>> rel="nofollow" or rel="author". According to the current processing steps of
>> RDFa 1.1, if this kind of @rel is used in an element containing a property
>> attribute (such as an RDFa Lite snippet), it can impact the processing and
>> change the triples which are generated. I'd like to explore ways to avoid
>> this in HTML+RDFa.
>> 
>> First of all let's start with an example:
>> <p vocab="http://schema.org/" typeof="Person">
>>    My name is <a href="http://example.com/" property="homepage">Stéphane
>> Corlosquet</a>.
>> </p>
>> 
>> which generates:
>> <> a schema:Person;
>>    schema:homepage <http://example.com/>.
>> 
>> Add a @rel to the mix:
>> <p vocab="http://schema.org/" typeof="Person">
>>    My name is <a href="http://example.com/" property="homepage"
>> rel="nofollow">Stéphane Corlosquet</a>.
>> </p>
>> 
>> and @property no longer targets the @href but the innerText instead:
>> <> a schema:Person;
>>    schema:homepage "Stephane Corlosquet";
>>    schema:nofollow <http://example.com/>.
>> 
>> 
>> Option #1: ignore @rel if it only includes HTML Link types as defined
>> at http://www.w3.org/TR/html5-author/links.html#linkTypes
>> 
>> Option #2: ignore @rel if it does not include any explicit CURIE. I think
>> it's safe to assume that the intentional use of RDFa terms in @rel will be
>> limited in comparison to the use of RDFa Lite and the new @property
>> behavior. Therefore requiring CURIEs to be used in @rel would allow us to
>> detect whether @rel is used in an RDFa context or not, and from there decide
>> whether it should be ignored or not.
>> 
>> In both options, it is important to emphasize the "ignore", as an empty @rel
>> would still have the same effect of switching the behavior of @property to
>> the old way.
> 
> BTW, the HTML5 specification contains similar text [1].  If you look
> at section "4.12.4.14 Other link types", you'll see that it references
> a micoformats document [2].  There it defines other "allowed" and "not
> allowed" values.  It categorizes the IANA link relations [1] as for
> non-HTML documents even though IANA's registry contains relations
> listed in section 4.12.4.
> 
> This feels like a slippery slope.  The list of "to ignore" values may
> change and it also contains useful like relations like "license",
> "alternate", "bookmark", and "tag".
> 
> The problem here is from allowing @property to take on dual role that
> depends on the presence of @rel or @rev and/or @src, @href, and
> @resource attributes.   When the @rel and @rev are present on an
> element with a link (i.e. @src, @href, or @resource), the @property is
> a shorthand for wrapping the descendants with markup and having the
> @property attribute there.
> 
> In the example, that is:
> 
> <p vocab="http://schema.org/" typeof="Person">
>    My name is <a href="http://example.com/" rel="nofollow"><span
> property="homepage">Stéphane Corlosquet</span></a>.
> </p>
> 
> Clearly, that is very different.
> 
> In step 11 of section 7.5 Sequence, what is the purpose of disallowing
> the same interpretation?  Why not just remove @rel and @rev from
> "otherwise, if the @rel, @rev, and @content attributes are not
> present, as a resource obtained from one of the following:" so that we
> get the triples:
> 
> <> a schema:Person;
>    schema:homepage <http://example.com/>;
>    schema:nofollow <http://example.com/>.
> 
> ?
> 
> [1] http://www.w3.org/TR/html5/links.html#following-hyperlinks-0
> [2] http://microformats.org/wiki/existing-rel-values#HTML5_link_type_extensions
> [3] http://www.iana.org/assignments/link-relations/link-relations.xml
> 
> 
> 
> -- 
> --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 16:56:18 GMT

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