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Re: [Fwd: Re: [DTB] Datatypes and Built-ins first run to clean up and extend the initial list]

From: Michael Kifer <kifer@cs.sunysb.edu>
Date: Mon, 03 Mar 2008 23:51:53 -0500
To: axel@polleres.net
Cc: "Public-Rif-Wg (E-mail)" <public-rif-wg@w3.org>
Message-ID: <7693.1204606313@cs.sunysb.edu>


> >>> A given IRI is interpreted as some abstract object in a given 
> >>> interpretation.  I do not understand how a casting function for 
> >>> such abstract objects can be defined in a meaningful way.
> >> 
> >> yes, it seems hairy/impossible to define it properly within the 
> >> current FLD framework, because I can, even if I assume fixed 
> >> interpretations for cast-functions, not "access" the lexical
> >> representation from this fixed interpretation...
> > 
> > It seems to me that the problem is with an inappropriate use of IRIs.
> >  You seem to be treating them as a data type, while IRIs are like RDF
> >  resources, and thus are not data types. Maybe you need to introduce
> > a data type for what you want (not sure).
> 
> hmmmm. ouch.
> Just to clarify a point here: It is not *me* who is treating IRIs like 
> datatypes here, it is just how it is done in FOAF and in other RDF 
> vocabularies... most actually. not my fault.

I am just elaborating on the problem that Jos pointed out.


>   To avoid this misunderstanding, I had quoted the FOAF spec in my 
> original mail in the part which was cut out in the reply::
> 
> > foaf [1] suggests to encode telephone numbers as rdf:resources using
> > a tel: scheme qualified URI:
> > 
> > "Property: foaf:phone phone - A phone, specified using fully
> > qualified tel: URI scheme (refs:
> > http://www.w3.org/Addressing/schemes.html#tel)."
> > 
> > in all RDF encodings of vCard I am aware of telephone numbers are
> > encoded in String literals, instead.
> > 
> > Now, if there is no way to get out the actual string of that URI in a
> > builtin, I have no clue how to address this simple ontology mapping
> > use case, see also [2], slide 4 and slide 10.
> > 
> > I don't want to go into the philosophical problem of that URLs and
> > URIs are intermingled in that FOAF encoding of telephone numbers, I
> > just want to write a rule which does that mapping.
> 
> This was my original question, how do I do this mapping from
> URIs to strings, if I need to (e.g. asking for a certain substing 
> appearing in a URL)? yes, this mapping is not possible in the datatype 
> system of FLD at the moment.
> 
> So, what do we want? Do we want to fix this, or do we want to convince 
> all people out there who use RDF in that way that they are doing wrong,
> i.e. shall I change my foaf file from


I do not know. If they really mean rdf:resource then they have a semantic
problem (I think it does not sit well with RDF semantics). But in your
example below you seem to be using the xsd:anyURI *data type* -- not an
rdf:resource -- to encode phone numbers. That has no problem. You can
define a builtin that operates on anyURIs.


	--michael  


> <http://www.polleres.net/foaf.rdf#me>
>     foaf:phone <tel:+35391495723> ;
>     foaf:homepage <http://www.polleres.net/> .
> 
> to
> 
> <http://www.polleres.net/foaf.rdf#me>
>       foaf:phone    "tel:+35391495723"^^xsd:anyURI ;
>       foaf:homepage "http://www.polleres.net/"^^xsd:anyURI .
> 
> So how do I convince all the rest of the world to change that likewise?
> Even the RDF Primer [2] (Example 6):
> ----------------------------------------------------------------------
>       <rdf:Description rdf:nodeID="abc">
>          <exterms:fullName>Dave Beckett</exterms:fullName>
>          <exterms:homePage rdf:resource="http://purl.org/net/dajobe/"/>
>       </rdf:Description>
> ----------------------------------------------------------------------
> 
> or the SPARQL spec [3] (examples in Section 6):
> 
> ----------------------------------------------------------------------
>   @prefix foaf:       <http://xmlns.com/foaf/0.1/> .
>   @prefix rdf:        <http://www.w3.org/1999/02/22-rdf-syntax-ns#> .
> 
>   _:a  rdf:type        foaf:Person .
>   _:a  foaf:name       "Alice" .
>   _:a  foaf:mbox       <mailto:alice@example.com> .
>   _:a  foaf:homepage   <http://work.example.org/alice/> .
> ----------------------------------------------------------------------
> 
> promote the use of rdf:resources for URLs (homepages, email-adresses, 
> etc.). It might be arguable with respect to the concepts, but people 
> *do* use URIs like that and it is even done in the specs of RDF as we 
> see here.
> 
> How do we cater for it?  By just stating I cannot get a substring out of 
> a homepage-URL or email-address... just because rdf:resource (and 
> rif:iri, respectively) are not datatypes?
> 
> I knew somehow why I put that in my signature ;-)
> 
> Axel
> 
> 
> 1. http://xmlns.com/foaf/spec/
> 2. http://www.w3.org/TR/REC-rdf-syntax/
> 3. http://www.w3.org/TR/rdf-sparql-query/
> 
> -- 
> Dr. Axel Polleres
> email: axel@polleres.net  url: http://www.polleres.net/
> 
> rdfs:Resource owl:differentFrom xsd:anyURI .
> 
Received on Tuesday, 4 March 2008 04:52:11 GMT

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