Re: reified statements in Turtle

AFAIK, your interpretation is correct, and RDF/XML does give you a convenient way of creating reified statements. It is extremely rarely used. This is also mentioned in the 2004 edition of the RDF Primer:

http://www.w3.org/TR/rdf-primer/#reification

Ivan



On Oct 15, 2013, at 14:31 , Eric Prud'hommeaux <eric@w3.org> wrote:

> I got an action item last week to send a reply to a CR comment asking
> for statements identifiers in Turtle. I wrote up the reply below but
> I'd like to check with the WG to see if my understanding of RDF/XML
> is correct:
> 
> RDF/XML parsing rules like resourcePropertyElt say that a statement
> *is* reified.
> [[
> If the rdf:ID attribute a is given, the above statement is reified
> with i := uri(identifier := resolve(e, concat("#", a.string-value)))
> using the reification rules in section 7.3 and e.subject := i
> ]] — <http://www.w3.org/TR/2004/REC-rdf-syntax-grammar-20040210/#resourcePropertyElt>
> Section 7.3 says to "add the following statements to the graph".
> <http://www.w3.org/TR/2004/REC-rdf-syntax-grammar-20040210/#section-Reification>
> , (the entailment of which is only the reified triples).
> 
> So parsing
> [[
> <Foo rdf:ID="bar"><baz ID="r1">bip</baz></Foo>
> ]]
> yields
> [[
> <#bar> a <Foo> ; <baz> "bip" .
> <r1> a rdf:Statement ;
>  rdf:subject <#bar> ;
>  rdf:predicate <baz> ;
>  rdf:object "bip" .
> ]], right?
> 
> It appears that IDs can appear on all types of propertyElt
> <http://www.w3.org/2013/10/rdfxml.rnc#rnc_propertyElt> (my annocated
> copy of the rnc 'cause why not have hyperlinks? feel free to add to
> re-publication of RDF/XML.) and on nodeElement, where they don't have
> a reification implication. So RDF/XML provides a convenient syntax to
> auto-reify every arc except:
> 
>  list arcs, i.e. rdf:first, rdf:rest.
>  type arcs from non-rdf:Description tags in a nodeElement.
>  arcs from the bnode implied by parseType="Resource".
>  arcs from the bnode implied by non-RDF attributes in a nodeElement.
> 
> (I note that parseTypeCollectionPropertyElt doesn't mention idAttr
> <http://www.w3.org/TR/2004/REC-rdf-syntax-grammar-20040210/#parseTypeCollectionPropertyElt>
> so presumably the reification is on the arc to the head of the list.)
> 
> 
> To: "Dr. A. Joseph Rockmore" <rockmore@cyladian.com>
> Cc: public-rdf-comments@w3.org
> Subject: Re: reified statements in Turtle
> In-Reply-To: <FD3A070D-522D-4B3F-80F5-32057C58FB52@cyladian.com>
> Date: ideally last month
> 
> * Dr. A. Joseph Rockmore <rockmore@cyladian.com> [2013-09-17 14:34-0700]
>> i don't know if the period for comments on the turtle recommendation are closed (the w3.org web site is a bit inconsistent), but in case its not, i'd like to offer the following.
>> 
>> i would like to strongly suggest that the turtle recommendation include statement identifiers for reification.  in the work i am doing it is imperative to maintain provenance on all statements, and the only way i have been able to do this in turtle is via explicit reification, such as:
>> 
>> foo:statement1 a rdf:Statement ;
>> 	rdf:subject thingID1 ;
>> 	rdf:predicate propertyID1 ;
>> 	rdf:object value1 ;
>> 	foo:source value 2 ;
>> 	foo:dateAsserted value 3 ;
>> 	etc.
>> 
>> this is ugly and overly verbose.  we would like a mechanism like in RDF/XML that supports expressing the statementID explicitly so that reified statements can be made about the statement, without having to express the statements regarding the subject, predicate, and object separately.
>> 
>> thank you for considering this addition.
> 
> Dear Joe,
> 
> Thank you for your comment. I'm sorry to say that for the reasons
> below, the RDF WG has decided not to develop a shorthand syntax for
> reified statements in Turtle:
> 
>  There are no existing proposals. The Turtle REC will reflect current
>  practice in existing Turtle parsers/serializers, except where the
>  language is evolving to towards compatibility with SPARQL.
> 
>  The community is mostly using named graphs to address the use cases
>  for which reification was intended.
> 
>  The RDF WG is almost at the end of its charter. Any changes at all
>  would make if difficult to publish a Recommendation before the WG
>  closes. A re-design of the language to enable reification would
>  likely take a long time.
> 
> -- 
> -ericP, on behalf of the RDF Working Group
> 
> 
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> 
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Ivan Herman, W3C 
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