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

From: Pat Hayes <phayes@ihmc.us>
Date: Sat, 27 Jul 2013 13:05:07 -0500
Cc: Eric Prud'hommeaux <eric@w3.org>, "www-archive@w3.org" <www-archive@w3.org>, "Peter F. Patel-Schneider" <pfpschneider@gmail.com>, Sandro Hawke <sandro@w3.org>, Andy Seaborne <andy@apache.org>
Message-Id: <616A0CE1-1C6F-4770-BE5A-09833223E146@ihmc.us>
To: Jeremy J Carroll <jjc@syapse.com>

On Jul 26, 2013, at 5:21 PM, Jeremy J Carroll wrote:

> Ah, and I just came across some other relevant text:
> 
> http://www.w3.org/TR/2013/REC-sparql11-query-20130321/#namedGraphs
> 
> The FROM NAMED syntax suggests that the IRI identifies the corresponding graph, but the relationship between an IRI and a graph in an RDF dataset is indirect. The IRI identifies a resource, and the resource is represented by a graph (or, more precisely: by a document that serializes a graph).
> 

I have no idea what this resource/graph distinction is intended to mean (and I never have understood it: to me, it reads as incoherent, as written.) But in any case, this text uses the term "identifies" rather than "denotes" or "refers to". See http://www.w3.org/TR/rdf11-mt/#notation-and-terminology

"The words denotes and refers to are used interchangeably as synonyms for the relationship between an IRI or literal and what it refers to in a given interpretation, itself called thereferent or denotation. IRI meanings may also be determined by other constraints external to the RDF semantics; when we wish to refer to such an externally defined naming relationship, we will use the word identify and its cognates. For example, the fact that the IRI http://www.w3.org/2001/XMLSchema#decimal is widely used as the name of a datatype described in the XML Schema document [XMLSCHEMA11-2] might be described by saying that the IRI identifies that datatype. If an IRI identifies something it may or may not refer to it in a given interpretation, depending on how the semantics is specified. For example, an IRI used as a graph name identifying a named graph in an RDF dataset may refer to something different from the graph it identifies."

We did that deliberately, for exactly this reason: the word "identifies" has been used all over the W3C (and other) documents with a wide variety of meanings, and it is impossible to interpret all of them as actual denotation. 

> 
> Given that the text in bold is already normative, am I detecting some part of the RDF WG that somehow wishes to go back on that. I do not believe that my ideal outcome would be no more than the text in bold.

But (I am guessing) you want it to be interpreted as meaning, the IRI actually refers to the graph. Which is exactly the semantic specification that we were unable to agree upon. 

Pat

> 
> 
> 
> Jeremy J Carroll
> Principal Architect
> Syapse, Inc.
> 
> 
> 
> On Jul 26, 2013, at 9:37 AM, Jeremy J Carroll <jjc@syapse.com> wrote:
> 
>> 
>> I slept on Eric's question for several days .
>> 
>> I ended up realizing that another aspect of the current drafts that I feel should change a bit is:
>> 
>> https://dvcs.w3.org/hg/rdf/raw-file/default/rdf-mt/index.html#rdf-datasets
>> 
>> "When a graph name is used inside RDF triples in a dataset it may or may not refer to the graph it names. The semantics does not require, nor should RDF engines presume, without some external reason to do so, that graph names used in RDF triples refer to the graph they name."
>> 
>> I would like some mechanism which indicates clearly that in my case it MAY refer to the graph it names, and I am proposing that
>> 
>> <uuu> rdf:type rdfs:Graph
>> 
>> be such a mechanism, and this be understood with intensional semantics like rdfs:Class rather than with extensional semantics like owl:Restriction
>> 
>> 
>> i.e. if in any graph in a dataset, there is such a triple, and we have an interpretation of that graph, and that the dataset does include a graph named <uuu> then it is pretty clear that the intent is that I am talking about the graph, and I would like the recommendations to say that in such interpretation it is this graph that we are talking about.
>> 
>> Jeremy J Carroll
>> Principal Architect
>> Syapse, Inc.
>> 
>> 
>> 
>> On Jul 19, 2013, at 9:06 PM, Eric Prud'hommeaux <eric@w3.org> wrote:
>> 
>>> On Jul 19, 2013 2:10 PM, "Jeremy J Carroll" <jjc@syapse.com> wrote:
>>> >
>>> > Sorry, I am failing to be brief ...
>>> >
>>> > On Jul 19, 2013, at 9:35 AM, Jeremy J Carroll <jjc@syapse.com> wrote:
>>> >
>>> >> [[[
>>> >>
>>> >> rdfs:Graph
>>> >>     
>>> >> rdfs:Graph is the class of graphs. All instances of rdfs:Graph correspond to the RDF model of a graph described in the RDF Concepts specification [RDF-CONCEPTS]. 
>>> >> An instance of  rdfs:Graph MAY also be described in an RDF dataset, in which case the triples in the graph SHOULD/MUST be the triples as specified in the dataset.
>>> >>
>>> >> ]]]
>>> >>
>>> >>
>>> >> (I would be happy with either SHOULD or MUST)
>>> >
>>> >
>>> > looking again, MUST is too strong - since this would allow anyone to modify anyone's else's intent. We need to qualify which RDF datasets and reduce the MUST down to SHOULD.
>>> > e.g. "MAY also be described in a related RDF dataset, .. SHOULD ." with the complete modified suggested text as
>>> >
>>> > [[[
>>> >
>>> > rdfs:Graph
>>> >     
>>> > rdfs:Graph is the class of graphs. All instances of rdfs:Graph correspond to the RDF model of a graph described in the RDF Concepts specification [RDF-CONCEPTS]. 
>>> > An instance of  rdfs:Graph MAY also be described in a related RDF dataset, in which case the triples in the graph SHOULD be the triples as specified in the dataset.
>>> >
>>> > ]]]
>>> 
>>> Sorry to be dim here, but does "the triples as specified in the dataset" indicate a truth predicate of some sort (in which case I would have expected "indicated" instead of "specified"). Or maybe I'm misinterpreting a signal that another graph (probably the default graph) includes all of the triples in the identified graph.
>>> 
>> 
> 

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Received on Saturday, 27 July 2013 18:05:34 UTC

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