Re: Re: further on ISSUE-39

(I have added a subject line with the issue numbering for the tracker. Somehow this got lost in the thread:-(


On Aug 12, 2010, at 16:22 , Richard Cyganiak wrote:

> 
> On 12 Aug 2010, at 14:31, Ivan Herman wrote:
>> I just want to understand this: did you propose to change the term mapping approach to something like:
>> 
>> <blabla> rdfa:term "something"
>> 
>> whereas leaving the prefix mapping the way it is now in the document? This was not really clear.
> 
> I am very concerned about term mappings, because I believe that the deployment story for RDFa 1.1 and onwards will be mostly about profiles with term mappings.
> 

Future will tell... and you are not alone with this prediction.

> I see prefix mappings as less critical, their main use IMO is to keep the old RDF-heads happy. I don't really have an opinion on their modelling. My intuition is that they are syntactical, while term mappings say something meaningful about classes and properties. I found Toby's examples below compelling.

I would still want to understand where do you wish to go. You say Toby's examples below are compelling, and he definitely argues for keeping the current structure for prefixes. Do you propose to have a different approach for terms than for prefixes? That might be very confusing in my view.

You also said (in your other mail) that you do not feel Toby's arguments are valid for terms, only for prefixes. To change his examples a bit: if I have a term definition

<http://www.ex.org/vocab/1.0/MyTerm> rdfa:term "exampleTerm" .

and, through some evolution of the vocabulary we have a 2.0 version, but this has a bridge of the form

<http://www.ex.org/vocab/1.0/MyTerm> owl:sameAs <http://www.ex.org/vocab/2.0/MyTerm> .

That, actually, means that I can also deduce a triple of the form

<http://www.ex.org/vocab/2.0/MyTerm> rdfa:term "exampleTerm" .

So how do we handle that? Unless we can, somehow, formally _restrict_ the effect of an rdfa:term predicate on a specific graph somehow (that may be a possibility but I am not 100% sure how to do that, but maybe we can), this may create the same type of issues as the ones Toby is referring to.

So. Trying to move forward... The RDFa Core document is already juggling with the term "graph". It talks about default graph, the processor graph, etc. Ie, we can very well refer to the profile graph for a specific document. We could then make it very explicit in the RDFa Core spec that only those triples are considered that are part of that graph; this would take away this problem (as well as Toby's problem). Yes, we are bringing a closed world in through the back door:-)

I must honestly admit that I still feel uneasy about the change, though. But trying to find a way forward...

Ivan


> 
> Best,
> Richard
> 
> 
>> 
>> Ivan
>> 
>>> Best,
>>> Richard
>>> 
>>> 
>>> On 12 Aug 2010, at 10:24, Toby Inkster wrote:
>>> 
>>>> On Fri, 6 Aug 2010 07:40:04 +0200
>>>> Ivan Herman <ivan@w3.org> wrote:
>>>> 
>>>>> This was discussed several times on the mailing list and I fully
>>>>> understand your issues. Here is the reason I was in favour of the
>>>>> current setup, but I am absolutely open to discussion because, well,
>>>>> it does complicate processing (speaking as an implementer).
>>>> 
>>>> FWIW, I agree with your reasoning for the current vocab. Prefix and term
>>>> mappings are semantically a relationship between two strings.
>>>> 
>>>> Imagine this:
>>>> 
>>>> 	<http://xmlns.com/foaf/0.1/> rdfa:prefix "foaf" .
>>>> 
>>>> Now, the following is also true (probably):
>>>> 
>>>> 	<http://xmlns.com/foaf/0.1/>
>>>> 	  a owl:Ontology ;
>>>> 	  owl:sameAs <http://dbpedia.org/resource/FOAF_(software)> .
>>>> 
>>>> Thus it follows that:
>>>> 
>>>> 	<http://dbpedia.org/resource/FOAF_(software)>
>>>> 	  rdfa:prefix "foaf" .
>>>> 
>>>> Thus an RDFa processor could expand 'foaf:name' to:
>>>> 
>>>> 	<http://dbpedia.org/resource/FOAF_(software)name>
>>>> 
>>>> Which we wouldn't want to happen.
>>>> 
>>>> In RDF terms, when we're defining prefixes and terms we're not
>>>> describing the underlying resources - we're just talking about
>>>> the xsd:strings. We're not even talking about xsd:anyURIs, because
>>>> say, "htt" is a valid expansion for a prefix, which might be used
>>>> as follows:
>>>> 
>>>> 	prefix="h: htt"
>>>> 	property="h:p://xmlns.com/foaf/0.1/"
>>>> 
>>>> So I'd recommend keeping the current pattern, though I think the
>>>> range of rdfa:uri should be changed to xsd:string for the above
>>>> reason.
>>>> 
>>>> Another argument against switching to
>>>> 
>>>> 	<http://xmlns.com/foaf/0.1/> rdfa:prefix "foaf" .
>>>> 
>>>> would be the fact that you'd lose the owl:FunctionalProperty-ness of
>>>> rdfa:prefix and rdfa:term.
>>>> 
>>>> -- 
>>>> Toby A Inkster
>>>> <mailto:mail@tobyinkster.co.uk>
>>>> <http://tobyinkster.co.uk>
>>>> 
>>>> 
>>> 
>> 
>> 
>> ----
>> Ivan Herman, W3C Semantic Web Activity Lead
>> Home: http://www.w3.org/People/Ivan/
>> mobile: +31-641044153
>> PGP Key: http://www.ivan-herman.net/pgpkey.html
>> FOAF: http://www.ivan-herman.net/foaf.rdf
>> 
>> 
>> 
>> 
>> 
> 
> -- 
> Linked Data Technologist • Linked Data Research Centre
> Digital Enterprise Research Institute (DERI), NUI Galway, Ireland
> http://linkeddata.deri.ie/
> skype:richard.cyganiak
> tel:+353-91-49-5711
> 
> 


----
Ivan Herman, W3C Semantic Web Activity Lead
Home: http://www.w3.org/People/Ivan/
mobile: +31-641044153
PGP Key: http://www.ivan-herman.net/pgpkey.html
FOAF: http://www.ivan-herman.net/foaf.rdf