Re: Formalism to generate a URI as an object?

Ivan,

In the latest Editor's draft <http://www.w3.org/2001/sw/rdb2rdf/r2rml/>, 
we have removed the <> from IRI values and _: from the blank node 
values. Instead, a new property, rr:termtype is used to designate the 
type of RDF term (IRI, BlankNode, or Literal).

Thanks,
- Souri.

On 11/1/2010 11:48 AM, Ivan Herman wrote:
> I am not sure whether this is a comment pointing at an issue in the document, or whether it is my own misunderstanding, in which case this is a question rather than a comment...
>
> Looking at the example A.2.2, the mapping to a logical table maps the original table to cells that include a URI using the NTriple '<...>' syntax. E.g., it maps the 'job' column to the jobTypeURI column with the cell becoming<xyz.com/emp/job/CLERK>  in the example. Then the mapping specification includes
>
> rr:propertyObjectMap [ rr:RDFTypeProperty emp:jobtype; rr:column "jobTypeURI" ]
>
> which means that the final triple will use  xyz.com/emp/job/CLERK as URI for an RDF class.
>
> What bothers me is that there seems to be a conceptual mixture of a particular syntax of RDF URI Resources (namely NTRiples) that encloses the URI in the '<' and'>' characters, and the fact that rr:RDFTypeProperty automatically maps on an RDF Resource whose URI is xyz.com/emp/job/CLERK. This should not be the case.
>
> Although the example does not have that, what if I wanted to generate the extra triple
>
> <xyz.com/emp/7369>  ivan:bla<xyz.com/emp/job/CLERK>  .
>
> My reading of the spec is that what I would have to do is
>
> rr:propertyObjectMap [
>      a rr:IRIMap ;
>      rr:property ivan:bla ;
>      rr:column "jobTypeURI"
> ]
>
> But that is then confusing: the value of the jobTypeURI cell is the string '<xyz.com/emp/job/CLERK>', so the system has to know that it has to strip the'<' and'>' characters to produce the Resource with the URI 'xyz.com/emp/job/CLERK'. Or is it so that the system always and automatically understands the syntax of the form'<xyz.com/emp/job/CLERK>' to be a string for an RDF URI Resource? What if I want to store, in my graph, the<xyz.com/emp/job/CLERK>  as a Literal? What is then the usage and the reason of having rr:IRIMap?
>
> I think the correct way is if the logical table mapping does
>
>     ('xyz.com/emp/job/'|| job) AS jobTypeURI
>
> the system has enough information both for the rr:IRIMap class and the rr:RDFTypeProperty provides enough information for the system to know that a URI resource should be created. The '<' and the'>' characters should not be used.
>
> I have the same issue with the way blank node ID's are explicitly created using the '_:' syntax. Again, if one uses the rr:BlankNodeMap then the system knows that the identifier in the cell must be used to generate a blank node. Mixing the NTRiple syntax into the mapping is unnecessary for my taste.
>
> Ivan
>
>
> ----
> Ivan Herman, W3C Semantic Web Activity Lead
> Home: http://www.w3.org/People/Ivan/
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