Re: Many-to-Many table in R2RML

Richard,

Thanks for all you work!


On Fri, Jul 29, 2011 at 2:09 PM, Richard Cyganiak <richard@cyganiak.de>wrote:

> On 29 Jul 2011, at 15:19, Juan Sequeda wrote:
> > Could you please add this example (or something similar) to the specs. I
> think it would be really useful.
>
> Done: http://www.w3.org/2001/sw/rdb2rdf/r2rml/#example-m2m
>
> I also broke up the example section into several smaller subsections to
> allow easier linking to specific parts of the example.
>
> It raises a question though: Why does the example in 2.5 use a referencing
> object map, while 2.6 just directly uses the same templates as the
> referenced tables? I don't know how to explain that well.
>

I'm guessing that there is a typo: the R2RML of example in 2.5 has is a
rr:objectMap when it should be a rr:RefObjectMap.

An explanation (or at least the way I see it): rr:refObjectMap is used for
attributes that are foreign keys that are part of non many-to-many tables.



> > ok. but if I'm not wrong, it's not explicit in the spec that you can give
> a subjectMap and objectMap a URI. or is it?
>
> I tried to clarify this a bit in 4.1
> http://www.w3.org/2001/sw/rdb2rdf/r2rml/#vocabulary
>
> [[
> An R2RML mapping graph […] may assign IRIs or blank node identifiers to any
> mapping component in order to enable re-use of mapping components within the
> mapping graph. For example, an IRI that represents a subject map may be used
> as the subject map of multiple triples maps; and may even be used as an
> object map of another triples map if it has the right properties.
> ]]
>

What do you mean by "if it has the right properties" ?

>
> I've also raised two issues regarding syntactic sugar:
> http://www.w3.org/2001/sw/rdb2rdf/track/issues/59
> http://www.w3.org/2001/sw/rdb2rdf/track/issues/60


+1

>
>
> Thanks for asking the question in the first place Juan -- it helps
> improving R2RML.
>

No problem.

Also, thanks for proposing how to re-draft the DM spec. I'm waiting for
Eric's and Alex's +1 so we can get that work done asap.


>
> Best,
> Richard