- From: Tomasz Pluskiewicz <tomasz.pluskiewicz@gmail.com>
- Date: Wed, 25 Jul 2012 19:24:10 +0200
- To: Juan Sequeda <juanfederico@gmail.com>
- Cc: Richard Cyganiak <richard@cyganiak.de>, David McNeil <dmcneil@revelytix.com>, public-rdb2rdf-comments@w3.org
It is what I have asked last month on http://answers.semanticweb.com/questions/16823/blank-nodes-as-subject-maps-in-r2rml Indeed it is for direct mapping, which I implement using a default mapping generator. Though I am still unsure how a subject map should look like for a direct mapping such as in http://www.w3.org/2001/sw/rdb2rdf/test-cases/#D005-1table3columns3rows2duplicates test case. It does indeed seem that each tuple generates a fresh blank node. If it were to only contain rr:termType and rr:class, then it is invalid in the light of current specifications as Richard notes. Otherwise I would like to ask for guidance what should such default mapping look like. Regard, Tomasz Pluskiewicz On Wed, Jul 25, 2012 at 7:05 PM, Juan Sequeda <juanfederico@gmail.com> wrote: > 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 17:25:19 UTC