Re: Direct Mapping

* 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

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

> >
> > > 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

Received on Monday, 6 September 2010 22:16:32 UTC