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Re: Graphs Design 6.2

From: Sandro Hawke <sandro@w3.org>
Date: Wed, 25 Apr 2012 11:19:17 -0400
To: Antoine Zimmermann <antoine.zimmermann@emse.fr>
Cc: public-rdf-wg@w3.org
Message-ID: <1335367157.9663.353.camel@waldron>
On Wed, 2012-04-25 at 16:30 +0200, Antoine Zimmermann wrote:
> 
> Le 25/04/2012 13:44, Sandro Hawke a écrit :
> > Here's a sketch of 6.2, which is similar to 6.1, but differs in the
> > areas where people have made me think they didn't like it.  I have not
> > put it on a wiki page or given it test cases yet.
> >
> > The differences are:
> >
> >    * Partial-graph semantics, instead of complete-graph semantics.  This
> > is more quad-like, and may be seen as more in keeping with RDF's usual
> > style of working with partial knowledge.   It makes it harder to reason
> > about what's unsaid, but few people are doing that anyway.
> 
> Both semantics could coexist, with an indicator making explicit which 
> one is assumed.

Perhaps, but I think that would probably be very confusing to users. 

> >    * A keyword "@union" may be given instead of the default graph,
> > indicating the default graph is the union of all the named graphs.  This
> > means everything in those graphs is asserted.    (Alternatively, we
> > could have "@asserted", perhaps parameterized by "all" or the names of
> > those graphs which are considered asserted.)
> 
> By "union", don't you mean "merge"?

I'm pretty sure I mean union, since the graphs need to share bNodes.
They are *not* supposed to be renamed apart. 

This is what people do in SPARQL, as I understand it.   It seems to be
required for the use cases like keeping track of inference.

> If so, I already made the very same proposal in my email showing how the 
> semantics of datasets [1] is addressing the use cases [2].
> 
> Unfortunately, this email was never discussed, nor commented, nor 
> replied to at all. I'm even wondering whether it has been read.

I read it, but the flow of events meant I didn't get to writing my
reply.   I think it was just before a telecon which pushed me in a
different direction.   My reply would have been along the lines of: "I
don't see how this would provide much interoperability.  I'd rather
provide interop among the whole community; this seems like it would
segment people into many different communities who can't talk to each
other.   Which of these @keywords would really be implemented by
everyone?"

> It annoys me a lot that my proposal seems to be disregarded, when Pat's 
> proposals, which have been always incomplete to various extent so far, 
> are always getting a lot of attention.

WG dynamics are strange and complicated.  I can never predict which of
my emails will be ignored and which will be carved into giant slabs of
stone.   (Some are also painted onto large wooden statues, then set on
fire.)  I try to just patiently come back to the points that seem more
important to me, when they're ignored, rephrasing and reframing them in
the hope that more people understand them.  One can also explicitly ask
the chairs to put it on the agenda.

     -- Sandro
> 
> [1] 
> http://www.w3.org/2011/rdf-wg/wiki/TF-Graphs/RDF-Datasets-Proposal#Semantics
> [2] http://lists.w3.org/Archives/Public/public-rdf-wg/2012Mar/0038.html
> 
> 
> >    * A class rdf:GraphAssociate containing all the things denoted by RDF
> > terms used as labels in datasets.     The label is an IRI or bNode, the
> > "associate" is the thing that IRI or bNode denotes.   The associate is
> > associated with the given graph.  This is a superclass of rdf:Graph,
> > because graphs have themselves as associates.   (I wouldn't mind a
> > better word, but haven't thought of one.)
> >
> >    * A class rdf:GraphContainer, a subclass of rdf:GraphAssociate.  A
> > GraphContainer differs from a Graph in that conceptually it can change
> > over time.   [We don't say anything about how to deal with it changing
> > over time, because (so far) RDF never talks about change-over-time.  If
> > it did (such as with rdf:starting and rdf:ending predicates) then that
> > solution would apply here as well.]   The trig document "{<u>  a
> > rdf:GraphContainer}<u>  {<a>  <b>  <c>  }" is true at exactly those times
> > that the Graph Container identified by "u" contains the triple expressed
> > as "<a>  <b>  <c>".    [Note well: I did not say "contains ONLY" that
> > triple.  Because of partial-graph semantics, the document is also true
> > if<u>  also contains some other triples.]
> >
> > The rest of 6.1 remains the same, including global-scope bNode labels,
> > bNodes allowed as graph labels, rdf:Graph, and rdf:hasGraph.   (I have
> > an idea for 6.3, but I don't have time to think it through before
> > today's meeting.)
> >
> >      -- Sandro
> >
> >
> >
> >
> >
> 
Received on Wednesday, 25 April 2012 15:19:30 UTC

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