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Re: Dataset Syntax - checking for consensus

From: Eric Prud'hommeaux <eric@w3.org>
Date: Wed, 26 Sep 2012 09:35:59 -0400
To: Antoine Zimmermann <antoine.zimmermann@emse.fr>
Cc: Pat Hayes <phayes@ihmc.us>, Sandro Hawke <sandro@w3.org>, W3C RDF WG <public-rdf-wg@w3.org>
Message-ID: <20120926133557.GA15570@w3.org>
* Antoine Zimmermann <antoine.zimmermann@emse.fr> [2012-09-26 09:23+0200]
> Le 26/09/2012 07:21, Pat Hayes a écrit :
> >
> >On Sep 25, 2012, at 9:28 PM, Sandro Hawke wrote:
> 
> <skip/>
> 
> >>>
> >>>>PROPOSED: Our dataset syntax will have some standard mechanism
> >>>>(to be determined within the next few weeks) through which a
> >>>>Dataset serialization can include some RDF data about the
> >>>>Dataset (that is, some metadata in the form of an RDF graph).
> >>>+1, but note that AFAIKS this requires semantics which will be
> >>>incompatible with some current use cases.
> >>
> >>Explain?
> >
> >OK, I will try again.
> >
> >People want to "label" a graph with a URI they are using to denote
> >something else, eg a person. The same URI cannot denote two things at
> >once. So the current proposal for a minimal semantics distinguishes
> >the thing denoted from the graph "named", by having a GR-EXT function
> >from things to graphs. But this means that when the URI is used in
> >RDF, it denotes the something else, not the graph. So you don't get
> >to use it in RDF metadata to refer to the graph. We could throw this
> >semantics away, and say that the name really does denote the graph it
> >"names", which has always made sense to me (and, apparently, to
> >Peter, who is arguing the case right now), but then it can't also
> >denote this other thing that people want it to denote, or perhaps
> >better, want to have the freedom to make it denote.
> >
> >I can't help observing that this very basic point about URIs and
> >naming has been bloody obvious since day one, and yet apparently this
> >WG is STILL, after over a year, unable to gets its collective head
> >around it.

...

> The current proposal is not inconsistent with what Sandro wants. You
> can say:
> 
> { <n> a sd:Graph;
>     eg:hasSomeMetadataProp <x> . }
> <n> {
>   #some triples
> }
> 
> Also, make it clear in the graph-metadata vocabulary that a sd:Graph
> is, say, a graph description. Oh, BTW, it already exists and it is
> on the verge of getting standardised. It's called SPARQL 1.1 Service
> description.
> 
> A quick look at the proposed semantics clearly shows that the
> example is consistent.

expanding the example to illustrate the dual use of the graph "identifier":

{ <Bob> a sd:Graph;
    eg:cached "2012009-26T11:25Z" . }
<Bob> {
  <Bob> a foaf:Person .
}

so <Bob> denotes the union of a person and a graph. 

Jeni Tennison talks about this in terms of a pun
  http://www.jenitennison.com/blog/node/170
but the root of the issue is good old http-range 14.
Two other range 14 resolutions are:

hash:
{ <Bob> a sd:Graph;
    eg:cached "2012009-26T11:25Z" . }
<Bob> {
  <Bob#me> a foaf:Person .
}

vs. slash:
{ <Bob> http:seeAlso <BobzPage> .
  <BobzPage> a sd:Graph;
    eg:cached "2012009-26T11:25Z" . }
<BobPage> {
  <Bob> a foaf:Person .
}

Both of these impose restrictions which a lot of existing data do not follow.


> <skip/>
> -- 
> Antoine Zimmermann
> ISCOD / LSTI - Institut Henri Fayol
> École Nationale Supérieure des Mines de Saint-Étienne
> 158 cours Fauriel
> 42023 Saint-Étienne Cedex 2
> France
> Tél:+33(0)4 77 42 83 36
> Fax:+33(0)4 77 42 66 66
> http://zimmer.aprilfoolsreview.com/
> 

-- 
-ericP
Received on Wednesday, 26 September 2012 13:36:36 GMT

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