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Re: rdfs:Graph ? comment on http://www.w3.org/TR/rdf11-concepts/#section-dataset and issue 35

From: Jeremy J Carroll <jjc@syapse.com>
Date: Mon, 16 Sep 2013 17:19:36 -0700
Cc: "public-rdf-comments@w3.org Comments" <public-rdf-comments@w3.org>
Message-Id: <F6F0E064-91B9-43CA-B2F2-8EE45BA6543B@syapse.com>
To: Sandro Hawke <sandro@w3.org>

On Sep 11, 2013, at 8:14 PM, Sandro Hawke <sandro@w3.org> wrote:

> On 09/11/2013 06:21 PM, Jeremy J Carroll wrote:
>> This section defines a vocabulary item rdf:Graph in addition to those in [RDF-SCHEMA].
>> This is the class of resources that are RDF graphs. If a resource in this class is identified by an IRI, and that IRI is used to name a graph in a dataset, then within that dataset the resource SHOULD correspond to the named graph.
> Does it not follow from this definition that:
>    PREFIX : <http://example.org/#>
>    PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>
>    :g1 :p 1.
>    :g1 a rdf:Graph.
>    :g2 a rdf:Graph.
>    GRAPH :g1 { :a :b :c }
>    GRAPH :g2 { :a :b :c }
> entails:
>    :g2 :p 1.
> (assuming the "SHOULD" is taken as something we can count on) ?

Hi Sandro

this is an excellent question, and one that I takes motivates your discussion of box-model on the WG mailing list.

I am not very comfortable with a YES, but, given the text I suggested a YES it would be.

In essence I think I want an intensional semantics rather than an extensional semantics, suggested text below; I start with philosophical discussion.

In maths, we typically refer to Sets with intensional semantics, in RDF we refer to classes with extensional semantics.

So if I have a class

jjc:Friends rdf:type rdfs:Class ;
      rdfs:comment "Jeremy's friends" .

and also a class

jjc:SandrosFriends rdfs:type rdfs:Class ;
      rdfs:comment "Sandro's friends" .

in the unlikely event that we have exactly the same friends, RDF semantics does not confuse the intent.

A view would be that RDF Semantics achieves this by moving the semantic intent more to the property rdf:type 

So, we could scrub the idea of having a class, and instead define a property.

An alternative proposed modification, which clarifies my desired NO to your entailment

3.7 The rdf:namesGraph property

This section defines a vocabulary item rdf:namesGraph in addition to those in [RDF-SCHEMA].

rdf:namesGraph is an instance of rdf:Property that is used to state that a resource is a name for a graph.

A triple of the form:

R rdf:namesGraph G

states that G is an RDF graph and R is a name for the graph G.
If R is an IRI, and that IRI is used to name a graph in a dataset, then within that dataset the resource G SHOULD correspond to the named graph.

The rdfs:domain of rdf:namesGraph is rdfs:Resource. No rdfs:range is specified.


With this my particular use case to add metadata about the graph as an intensional as opposed to an extensional object would be addressed as follows.

    PREFIX : <http://example.org/#>
    PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>
    GRAPH :g1 { :g1 rdf:namesGraph _:g ; rdfs:comment "An example graph" }

Jeremy J Carroll
Principal Architect
Syapse, Inc.

Received on Tuesday, 17 September 2013 00:20:09 UTC

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