Re: Keeping R2RML free of Direct Mapping dependency (ISSUE-25)

On Tue, Apr 26, 2011 at 10:46 AM, Ivan Herman <ivan@w3.org> wrote:

>
> On Apr 26, 2011, at 17:39 , Juan Sequeda wrote:
>
> > +1
> >
> > I've been wanting to state this for a while: have the Direct Mapping
> expressed has R2RML. I guess we can talk today about how we should proceed
> on this.
> >
> > IMO, this will be the starting point for users:
> >
> > Scenario 1:
> > 1) Generate Direct Mapping. The output will be a R2RML file
> > 2) Customize the R2RML file
> >
> > Scenario 2:
> > 1) Create views in the database of the data that I want to export
> (assuming I can create views)
> > 2) Generate a (customized) direct mapping. user can choose which
> tables/views want to be directly mapped
> > 3) Use RIF/SPARQL Construct
> >
> > I'm betting on Scenario 2. Assuming the user has create view privileges,
> IMO, it will be easier to create view and direct map, instead of learning
> R2RML. But this is my opinion (and what I'm betting on). Additionally, this
> "customized direct mapping" is not part of the spec. But I just wanted to
> get this use-case out there.
>
> I am not even sure what this customization means to be honest...
>

Just to make clear, this is out of the scope of the group... .

What I mean by customization is a UI that lets a user choose which
tables/views want to be directly mapped.

>
> However: scenario 2 presupposes that the user uses some additional tool at
> the end (RIF/SPARQL). If so, then I do not really see the value of that
> intermediate view. I have the impression that I can express everything I
> would do for a view via, say, RIF, SPARQL, or other tools that massage RDF
> data...
>

Actually, I never had thought about RIF/SPARQL till I saw that Eric was
talking about it.

Assuming your direct graph is the exact RDF graph you want to have (and you
can assume this if you create a view of the data you would like to expose),
then all you need is a 1-1 substitution of the direct mapping terms to the
terms of the domain ontology you would like to use. We simply have a simple
1-1 mapping file to do this. So a SPARQL query using the domain ontology
that you want, gets translated using the 1-1 mapping file into a SPARQL
query on the direct graph and then you are done.

These are implementation details of our system, and are out of the scope of
the group.


> Ivan
>
>
> >
> > Juan Sequeda
> > +1-575-SEQ-UEDA
> > www.juansequeda.com
> >
> >
> > On Tue, Apr 26, 2011 at 10:17 AM, Ivan Herman <ivan@w3.org> wrote:
> >
> > On Apr 26, 2011, at 17:11 , Alexandre Bertails wrote:
> >
> > > On Tue, 2011-04-26 at 09:53 -0500, David McNeil wrote:
> > >>
> > >>>
> > >>>> If the user wants a hybrid of these two models then they
> > >>        can generate the Direct Mapping for an RDB and then replace
> > >>        parts of it with a hand-crafted R2RML mapping.
> > >>>>
> > >>>
> > >>> I am not sure I understand that one. You mean generate an
> > >>        R2RML that would correspond to a Direct Mapping?
> > >>>
> > >>>
> > >>> What I mean is to use a Direct Mapping tool to produce an
> > >>        R2RML mapping file for an RDB.
> > >>
> > >>
> > >>        Yes, that is what I meant. An R2RML representation of the DM
> > >>        results for that particular RDB.
> > >>
> > >>        If we go down that route, it would be worthwhile having an
> > >>        appendix in either the r2rml or the dm document that gives a
> > >>        precise mapping of the dm to r2rml. This should not be left to
> > >>        implementers to be figured out separately.
> > >>
> > >> Agreed. I was thinking the Direct Mapping was expressed in terms of
> > >> R2RML, but I see now that is not the case.
> > >
> > > The Direct Mapping was never intended to be "expressed in terms of
> > > R2RML". But I agree that there could a section about it in the spec.
> > > Just remember this will never be the normative definition of the Direct
> > > Mapping. And the mapping itself will be parameterized by an instance of
> > > RDB.
> >
> > Agreed and agreed:-) It should be in an informative appendix of one of
> the two specs.
> >
> > Ivan
> >
> > >
> > > Alexandre.
> > >
> > >>
> > >> -David
> > >>
> > >
> > >
> >
> >
> > ----
> > Ivan Herman, W3C Semantic Web Activity Lead
> > Home: http://www.w3.org/People/Ivan/
> > mobile: +31-641044153
> > PGP Key: http://www.ivan-herman.net/pgpkey.html
> > FOAF: http://www.ivan-herman.net/foaf.rdf
> >
> >
> >
> >
> >
> >
> >
>
>
> ----
> Ivan Herman, W3C Semantic Web Activity Lead
> Home: http://www.w3.org/People/Ivan/
> mobile: +31-641044153
> PGP Key: http://www.ivan-herman.net/pgpkey.html
> FOAF: http://www.ivan-herman.net/foaf.rdf
>
>
>
>
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