Re: Direct Mapping

On Mon, Sep 6, 2010 at 5:15 PM, Eric Prud'hommeaux <eric@w3.org> wrote:

> * Juan Sequeda <juanfederico@gmail.com> [2010-09-06 16:57-0500]
> > >
> > >
> > >
> > > Let's see if I understand the implied mechanics. Option 1 directly
> > > specifies the RDF graph implied by a database (for any tuple in the
> > > database, you can say exactly what triples are in the direct
> > > graph). Option 2 specifies a mapping language, with certain mapping
> > > semantics, and with a default configuration. The default graph is the
> > > products of applying the mapping semantics for a default configuration
> > > to a database.
> > >
> > >
> > Option 2 uses R2RML.
> >
> > I see the two options this way
> >
> > Option 1:
> >
> > 1) We (the WG) present the direct mapping rules in order to generate a
> > direct RDF graph from a RDB
> > 2) Database vendors (oracle, db2, etc) implement these mapping rules OR
> > RDB2RDF systems on top of a RDB can read the database dictionary and run
> > these mapping rules
> > 3) You click the button "Generate Direct RDF"
>
> Or you say
>  dbview --serve http://localhost:8888/proteins --user XXX --password YYY
> db2pro.rif db2biopax.rif
> and issue SPARQL queries against http://localhost:8888/proteins .
>
> > 4) Outcomes your RDF
> > 5) Use RDF to RDF tools (sparql constructs, etc) to map to other
> > vocabularies
>


What is db2pro.rif and db2biopax.rif ?

The whole idea is for this to be completely automated. No input at all from
the user, right?

If the rif file is the RDF to RDF, then that is not part of the direct
mapping.


>  In the server scenario, they're part of the query transformation
> configuration, but yes, the effec is the same; the SPARQL queries
> operate over the same (virtual) graphs.
>
> > Option 2:
> >
> > 1) We (the WG) present the direct mapping rules in order to generate a
> > direct RDF graph from a RDB
> > 2) Database vendors (oracle, db2, etc) implement these mapping rules OR
> > RDB2RDF systems on top of a RDB can read the database dictionary and run
> > these mapping rules
> > 3) You click the button "Generate Direct RDF"
> > 4) Outcomes your RDF
> > 5) Out comes the R2RML mapping file that generated the Direct RDF Graph
> > 6) A user can modify the R2RML mapping file in order to change
> vocabularies,
> > etc
> >
> >
> > So.. if we agree on this.. we are practically then talking about the same
> > thing. Only difference is that in Option 2 we are outputing the direct
> > mapping also in R2RML. Otherwise.. why would we need R2RML??????
>
> I think the main reason folks want R2ML is to have an alternative to
> writing RIF rules for defining the e.g. biopax view.

Both approaches
> can be used to:
>  • generate SQL views on the server
>  • configure some intermediate agent to present the appropriate graph
>  • produce a materialized view
>


I still don't understand then why we are not expecting from the direct
mapping a R2RML mapping file that will produce the direct RDF graph


> > >
> > > > So you think that a direct mapping shouldn't output the R2RML file? I
> > > think
> > > > it should because this file is the basis for people to work on and
> start
> > > > customizing it.
> > >
> > > The RDF rules folks will have everything they need with option 1. They
> > > can write/share rules in RIF, SPIN, n3, ... which transform the
> > > default graph to popular ontologies. Simple implementations will
> > > materialize these graphs, and arguably cooler implementations will
> > > work directly on the relational data, but that's really implementation
> > > detail; all they need is the default graph.
> > >
> > >
> > > > > Hence I'm with Eric here.
> > > > >
> > > > >
> > > > >  The automatic mapping file that is generated in D2R is equivalent
> to
> > > the
> > > > >> Direct Mapping (right Richard?).
> > > > >>
> > > > >
> > > > > Well I'd say the *graph* produced by an auto-generated D2R mapping
> file
> > > is
> > > > > equivalent to the direct mapping.
> > > > >
> > > >
> > > > and I'd call the auto-generated D2R mapping file the Direct Mapping
> file.
> > > So
> > > > D2R does option 2 then.
> > > >
> > > > >
> > > > > Best,
> > > > > Richard
> > >
> > > --
> > > -ericP
> > >
>
> --
> -ericP
>