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Re: Named Graphs / Layers / Surfaces / Doohickies added to JSON-LD

From: Sandro Hawke <sandro@w3.org>
Date: Tue, 01 May 2012 08:32:41 -0400
To: Andy Seaborne <andy.seaborne@epimorphics.com>
Cc: public-rdf-wg@w3.org
Message-ID: <1335875561.27977.55.camel@waldron>
On Tue, 2012-05-01 at 12:38 +0100, Andy Seaborne wrote:
> 
> On 30/04/12 23:46, Sandro Hawke wrote:
> > On Mon, 2012-04-30 at 15:56 -0400, Manu Sporny wrote:
> >> Our intent when we started JSON-LD was to leave named graphs out of the
> >> spec. We were waiting on this group to finalize the modeling aspects of
> >> named graphs because we didn't want to do something counter to what this
> >> group was going to propose.
> >>
> >> We had been pushing back on requests to add named graphs to JSON-LD for
> >> quite some time and finally had to give in at the end because we had to
> >> understand how named graphs might affect the syntax in the future. We
> >> didn't want to paint ourselves into a corner. In the end, it was a
> >> fairly benign thing to add (from a syntax perspective), so we just went
> >> ahead and did it.
> >>
> >> Keep in mind that we go out of our way to not mention how advanced
> >> concepts like sharing bnode identifiers between named graphs works (or
> >> doesn't work). In other words, we specified the syntax for naming
> >> graphs, but have not really addressed any of the range issues since
> >> we're waiting on the RDF WG to propose something.
> >>
> >> Section 4.9 introduces the concept of a Named Graph in JSON-LD:
> >>
> >> http://json-ld.org/spec/latest/json-ld-syntax/
> >
> > I'm not quite sure I understand the syntax, but if my guesses are right,
> > it seems like a reasonable design.   Excellent.   Glad to hear JSON-LD
> > is ready for broader attention.
> >
> > Back on the subject of layers, I note that your use of the term "graph"
> > in this spec is, I think, evidence of the problem that's been causing us
> > such problems, and which I think the term "layers" solves:
> >
> >          This example says that there is a linked data graph identified
> >          by http://example.org/linked-data-graph which is composed of the
> >          statements about Manu and Gregg and a reference to another IRI,
> >          which could make statements about Markus.
> >
> > This text uses the word "graph" to mean g-box (now "layer", for me), not
> > to mean RDF Graph.   At least, I'm 99% sure it does.  It makes almost no
> > sense to talk about an RDF Graph that way, giving it a human-readable
> > HTTP URL.
> 
> It may be a manifestation of the fact Pat pointed out and has come up 
> several times, if the container is unchanging, using the name of the 
> container as a way to talk about the contents (the mapping being 1-1, 
> time invariant) is something we all do.

It might -- there are certainly applications for "static layers" -- but
I strongly doubt that's what the JSON-LD editors had in mind.   We could
tell better if they used a less "meta" URL; I think static layers
normally have inscrutable URLs with sequence numbers or hashes in them.

   -- Sandro

> 	Andy
> 
> 
Received on Tuesday, 1 May 2012 12:32:51 GMT

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