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Re: Blank nodes as subject maps in R2RML

From: Juan Sequeda <juanfederico@gmail.com>
Date: Wed, 25 Jul 2012 12:05:34 -0500
Message-ID: <CAMVTWDxGz-eOTJdZJrxerat41-+dGvR+UVX0DwH=6zYr53qf1Q@mail.gmail.com>
To: Richard Cyganiak <richard@cyganiak.de>
Cc: Tomasz Pluskiewicz <tomasz.pluskiewicz@gmail.com>, David McNeil <dmcneil@revelytix.com>, public-rdb2rdf-comments@w3.org
However, If this were to be valid, it would automatically generate a fresh
bnode for each tuple. Which would lead us to the whole discussion that we
had before about bnodes and the direct mapping.

Tomasz, is this a feature or something that you need?

Juan Sequeda
+1-575-SEQ-UEDA
www.juansequeda.com


On Wed, Jul 25, 2012 at 11:59 AM, Richard Cyganiak <richard@cyganiak.de>wrote:

> On 25 Jul 2012, at 15:05, Tomasz Pluskiewicz wrote:
> > Sorry to revive an old topic, but I have recenlty realized the root of
> > my question.
> >
> > The R2RML specs at http://www.w3.org/TR/r2rml/#dfn-term-map state
> > clearly that "A term map must be exactly one of the following: a
> > constant-valued term map, a column-valued term map, a template-valued
> > term map." Doesn't this mean that a term map
> >
> > <StudentsTriplesMap> rr:subjectMap
> > [
> >    rr:termType rr:BlankNode;
> >    rr:class <http://example.com/Student>
> > ];
> >
> > is in fact invalid, having no explicit rr:constant, rr:column or
> > rr:template property?
>
> It is indeed invalid. You'd usually want an rr:template or rr:column that
> creates the blank node identifier.
>
> Best,
> Richard
>
>
> >
> > Regards,
> > Tomasz
> >
> > On Fri, Jun 8, 2012 at 10:19 PM, Tomasz Pluskiewicz
> > <tomasz.pluskiewicz@gmail.com> wrote:
> >> Thank you for answering. Also, let me answer here again.
> >>
> >> I forgot to mention I intended the mapping as default mapping for
> >> table without primary key.
> >>
> >> In my oppinion by default direct mapping should generate a blank node
> >> for each row. And I do have mixed feelings about the behavior not
> >> preserving duplicate rows.
> >>
> >> Regards,
> >> Tomasz
> >>
> >> On Fri, Jun 8, 2012 at 6:26 PM, Juan Sequeda <juanfederico@gmail.com>
> wrote:
> >>> I asked on the forum, but let me ask here.
> >>>
> >>> are you expecting the R2RML engine to generate a blank node for each
> tuple,
> >>> or do you have a column value that you would like to use in order to
> >>> generate the blank node?
> >>>
> >>> Juan Sequeda
> >>> +1-575-SEQ-UEDA
> >>> www.juansequeda.com
> >>>
> >>>
> >>>
> >>> On Fri, Jun 8, 2012 at 9:22 AM, David McNeil <dmcneil@revelytix.com>
> wrote:
> >>>>
> >>>>> From the latest R2RML draft:
> >>>>
> >>>> * a subject map is a term map,
> >>>> http://www.w3.org/2001/sw/rdb2rdf/r2rml/#dfn-term-map
> >>>>
> >>>> * the termType property can be used on term maps,
> >>>> http://www.w3.org/2001/sw/rdb2rdf/r2rml/#termtype
> >>>>
> >>>> So "yes", you can use termType on subject maps and this is how you
> would
> >>>> produce subjects as blank nodes.
> >>>>
> >>>> -David
> >>>
> >>>
> >
>
>
Received on Wednesday, 25 July 2012 17:06:26 UTC

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