Re: Proposed Resolution for Issue 42

On Tue, May 31, 2011 at 3:25 PM, Richard Cyganiak <richard@cyganiak.de>wrote:

> On 31 May 2011, at 21:08, Juan Sequeda wrote:
> > Thinking quickly out loud... so please correct me if I'm wrong
> >
> > wouldn't we need rdfs:range triples for the case of reference triples:
> >
> > <Student/id=1> <enrolled> <Course/id=2>
>
> I don't think so. We already have in the direct graph:
>
>   <Course/id=2> a <Course>.
>
> That's sufficient to know that <Course/id=2> is the result of mapping a
> tuple in the Course table. The fact that <Course/id=2> occurs as the object
> of <Student#enrolled> is sufficient to infer the rdfs:range statement.
>
> An explicit rdfs:range triple would be more convenient, I don't dispute
> that :-) But not strictly necessary. So I'd prefer to keep this discussion
> separate from ISSUE-42.
>

Got it.


>
> In terms of process, I think it would be good if someone created an issue
> for these additional direct mapping schema triples, and put together a quick
> strawman on the wiki …
>

I can... but in a couple of days.

>
> Richard
>
>
> >
> >
> > Juan Sequeda
> > +1-575-SEQ-UEDA
> > www.juansequeda.com
> >
> >
> > On Tue, May 31, 2011 at 2:53 PM, Richard Cyganiak <richard@cyganiak.de>
> wrote:
> > Hi Alexandre,
> >
> > On 31 May 2011, at 20:27, Alexandre Bertails wrote:
> > >> I would agree to a proposal that maintains reversibility of the
> mapping by adding rdfs:domain triples to the properties, and does not
> generate triples for NULL values.
> > >
> > > I think that for the moment, we can agree on the current proposal
> > > without speaking about any concrete solution, which will come later
> when
> > > we're ready for it.
> >
> > No, because I'd like to know what I am agreeing to. I would likely be
> opposed to a solution that introduces a parliament of OWL into the direct
> mapping in order to work around the NULL issue.
> >
> > > rdfs:domain may be enough for this issue, but we may want other
> information as well.
> >
> > I think we all agree that rdfs:domain is *necessary*.
> >
> > I believe that it is also *sufficient* to reconstruct the NULLs, and have
> seen no claims to the contrary.
> >
> > So let's go with rdfs:domain *only* as the resolution to ISSUE-42.
> >
> > More schema triples may still be added to the direct mapping later on,
> but that needs to be discussed, and it can't be discussed before there's a
> proposal on the table. So I suggest treating additional schema triples as a
> different and separate issue (which someone should create in the tracker).
> >
> > PROPOSAL: Resolve ISSUE-42 by not creating triples for NULL values, and
> adding rdfs:domain statements to the direct mapping graph. This does not
> preclude adding more schema triples in a future resolution.
> >
> > Best,
> > Richard
> >
>
>