Re: Q: ISSUE-41 bNode semantics

Ok, looks like we are getting somewhere!

On Thu, May 19, 2011 at 3:38 PM, Enrico Franconi <>wrote:

> On 19 May 2011, at 22:30, David McNeil wrote:
> > Admittedly this is a long thread and it is hard to follow, but it seems
> to me that Richard is advocating omitting the NULL values from the Direct
> Mapping triples and that Enrico is ok with omitting the NULL values from the
> Direct Mapping, so maybe that is an approach that would have broad support?
> (This assumes that the Direct Mapping includes the schema information which
> it sounds like the Direct Mapping editors agree that it should).
> Indeed. Basically the schema information allows you to reconstruct the NULL
> values - as if you had them directly (which is admittedly easier, I guess;
> and this has been the choice of SQL).
> Note that a consequence of this is that the translated data alone is not
> meaningful anymore as an RDF graph in its solitude, but it should be coupled
> with schema information *and* a recipe on how to cook all this stuff
> together: you have to prescribe how queries should be translated in order to
> give the same/correct answer.


This means that we need to extend our Direct Mapping to translate the schema
into RDFs/OWL. And if you want to get the Nulls, you will need to use
Optionals in your sparql query.

> cheers
> --e.

Received on Thursday, 19 May 2011 20:46:07 UTC