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Re: Graphs Design 6.2

From: David Wood <david@3roundstones.com>
Date: Wed, 25 Apr 2012 08:40:25 -0400
Cc: public-rdf-wg <public-rdf-wg@w3.org>
Message-Id: <398ED75B-F30F-4FE1-86B2-B307EE67CF95@3roundstones.com>
To: Sandro Hawke <sandro@w3.org>
Hi Sandro,

On Apr 25, 2012, at 07:44, Sandro Hawke wrote:

> 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.  

Hmm, perhaps we don't agree after all on this.  I accepted your argument for *both* complete and partial graph semantics, as did Lee in his message about Anzo's implementation.  We differed on where, how and whether to allow a mechanism to choose.

Are you against choosing the type of semantics?  I may have missed some messages, although I've tried not to.

Regards,
Dave

> 
>  * 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.)
> 
>  * 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 12:40:59 UTC

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