Fwd: R2RML: classes of triples map only constants

Forwarding Ahmed's response to the public-rdb2rdf-comments list.


Begin forwarded message:

> From: Ahmed Bassiouni <ahmedbassi@gmail.com>
> Date: 8 November 2011 00:28:51 GMT
> To: Richard Cyganiak <richard@cyganiak.de>
> Subject: Re: R2RML: classes of triples map only constants
> 
> Hi Richard,
> Wording in docs now much better.
> Cheers,
> Ahmed
> 
> On Tue, Nov 8, 2011 at 3:42 AM, Richard Cyganiak <richard@cyganiak.de> wrote:
> Hi Ahmed,
> 
> Thanks for your comment on the R2RML Last Call draft.
> 
> The working group discussed your feedback. Our response is below. Could you please respond to this message and let us know if our response addresses your comment?
> 
> On 26 Sep 2011, at 03:28, Ahmed Bassiouni wrote:
> > Something I have noticed: is that the RDF types of a triples map (the "classes"), can only be constants.
> >
> > What happens in the scenario where you want a dynamic class, for example column-based. Take this scenario:
> >
> > Table Employees:
> > Emp_ID: 1234
> > EMP_Name: "John Smith"
> > EMP_Pay: "PartTimeEmployee"
> >
> > You want to assign the triples map two classes: one is Employee (constant) and the other is PartTimeEmployee (derived from a column).
> 
> The Last Call draft already answers this question in a Note in Section 6.2:
> 
> [[
> This property [rr:class] is merely a shortcut for specifying an rr:predicateObjectMap with predicate rdf:type and the rr:class IRI as a constant object. Mappings where the class IRI is not constant, but needs to be computed based on the contents of the database, can be achieved by defining such a rr:predicateObjectMap with a non-constant object.
> ]]
> http://www.w3.org/TR/2011/WD-r2rml-20110920/#typing
> 
> We found that the wording of this note could be improved, and changed it to:
> 
> [[
> Mappings where the class IRI is not constant, but needs to be computed based on the contents of the database, can be achieved by defining a predicate-object map with predicate rdf:type and a non-constant object map.
> ]]
> http://www.w3.org/2001/sw/rdb2rdf/r2rml/#typing
> (This is the latest Editor's Draft.)
> 
> > So I was wondering if you did not have this scenario in mind, or was the design intentional with a dynamic RDFtype assigned only through a separate predicate-object map??
> 
> We had this scenario in mind. That's why we added the note that explains how to handle this scenario.
> 
> Thanks again, and all the best,
> Richard
>