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RE: dataset semantics -- was Re: ACTION-278: grammar for TriG

From: Markus Lanthaler <markus.lanthaler@gmx.net>
Date: Mon, 8 Jul 2013 21:22:34 +0200
To: <public-rdf-wg@w3.org>
Message-ID: <01cf01ce7c10$832cb7f0$898627d0$@lanthaler@gmx.net>
On Sunday, July 07, 2013 6:51 PM, Sandro Hawke wrote:
> On 07/07/2013 08:48 AM, Markus Lanthaler wrote:
> >> Earlier, I gave the
> >> example that this could be flagged by having the triple { <> a
> >> rdf:BoundDataset } in the default graph. Another name for that might be
> >> "Direct".
> >
> > A more granular alternative would be to define rdf:Graph which could
> > be used to type things as "denoting graph name".
> 
> Yes, but that would require a whole lot of extra triples, for ever and
> ever.

True, but since when do we care about the amount of triples? We could even
have both where a rdf:BoundDataset in the default graph entails the
rdf:Graph triples.


> My guess is we'll converge on the Direct+Webview semantics below,
> and at some point it'll be flagged at some protocol layer so the dataset
> wont even need to be flagged internally.   At that point, it'll be as
> if we'd been able to properly address it all now.

Hmm... changing semantics at the protocol layer.. somehow this reminds me of
httpRange-14 :-P


> >> But this is too speculative to put into a document that's slated to
> >> become a REC by the end of the year.  So instead, dataset semantics are
> >> an extensibility point, and we can experiment for a while.
> >
> > ... probably leading to interoperability problems till we feel ready to
make
> > a decision at which point it probably is too late as we can't modify the
> > semantics of existing data anymore.
> >
> > Sorry for being so negative but I think we are making a huge mistake
> > here.
> 
> I agree it's a very uncomfortable, unfortunate situation.  I think
> there's a plausible path (outlined above) to a world where this is all
> okay.   Our current LC drafts keep us on that path, while giving us some
> flexibility to switch to other paths if this turns out to have a
> problem.
> 
> What would you propose we do today, instead?

I'm not sure but maybe doing exactly the opposite would be better, i.e., by
default graph names denote their graphs. If you don't want that, add a magic
triple to the default graph (rdf:UnboundDataset). I haven't analyzed the
consequences such an approach would have yet but from my feeling tells me
there shouldn't be too many bad surprises. It's simple enough to add such
triples in legacy applications which worked under that assumption.

What do you think about such an approach? Are there any negative side
effects you could think of?


--
Markus Lanthaler
@markuslanthaler
Received on Monday, 8 July 2013 19:23:09 UTC

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