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Re: [pedantic-web] Re: The OWL Ontology URI

From: Jonathan Rees <jar@creativecommons.org>
Date: Tue, 11 May 2010 14:38:49 -0400
Message-ID: <AANLkTimIbz1EFnQ8dSvaOiY65PFM66z4kk7BcHnsylU5@mail.gmail.com>
To: Pat Hayes <phayes@ihmc.us>
Cc: AWWSW TF <public-awwsw@w3.org>
On Mon, May 10, 2010 at 4:25 PM, Pat Hayes <phayes@ihmc.us> wrote:
> Let me give an intuitive case in support of the Nays here. An RDF graph is a
> set, which is not the same as a document, for sure. The *same* graph can be
> encoded in a variety of different syntactic forms. Consider two documents,
> one in RDF/XML, the other in NTriples, describing the same graph. If we
> identify the document with the graph it describes, then these have to be the
> same. But they aren't the same. So even if a graph is an information
> resource (and I agree that one can make out a case for that position), it
> certainly isn't the same information resource as any document (In RDF/XML or
> NTriples or any other notation) that represents it syntactically. So, one
> ought to use redirection to refer to it, according to http-range-14. So,
> whether its an information resource or not is kind of moot, since even if it
> is, it can't be directly identified by a URI which returns a 200 code.
>
> Pat

Suppose we have several things
  t1. An RDF/XML document / syntactic form / representation
  t2. An N-triples document / syntactic form / representation
  t3. An information resource that has t1 and t2 as "representations"
  t4. A graph that is serialized / encoded by t1 and t2
And we have a URI U such that GET U retrieves t1 and/or t2, and such
that U refers to t3.

We know that:
  - t3 has some of the same properties as t1 and t2 (e.g. authorship)
  - t3 is not the same as t1 or t2 (differs in some properties)
  - there are many IRs that could be t3, i.e. t3 isn't uniquely
determined by the above (e.g. could vary according to what *other*
representations exist, or by temporal behavior)

The question is whether t4 = t3 is consistent with what has been
decided about web architecture, and/or about "good practice" (which I
think is what you're getting at). I don't see anything in what you say
that would force yea or nay.

If it's inconsistent, that is interesting because it ought to tell us
something general about IRs, which are otherwise mysterious. (Graph is
just a stand-in for any number of other boundary cases, such as
journal article or referent-of-data:-URI or DOM tree or XML element or
XML infoset.)

If it's consistent, then why didn't they just do the obvious thing in
SPARQL and say that the graph URI refers to a graph? That's why I
assume the SPARQL authors determined somehow that graphs are not IRs
(although Dan's right, they don't come out and say so and it's not
forced).

TimBL has asserted that numbers, strings, and representations are not
information resources (despite fitting the AWWW definition perfectly,
IMO). Perhaps graphs are like numbers and strings somehow in being
deprived of IR-nature. It would be nice to know the details. Maybe the
time sheet example we talked about before bears on this case: if t5
and t6 "have" the same representations at all times, but t5 is Alan's
time sheet and t6 is my time sheet (we coincidentally work exactly the
same hours), they must be different resources since the have different
"meaning" (or "intent" or "phlogiston" per earlier discussion). Maybe
numbers, strings, representations, and graphs lack phlogiston, and
that's why they fail the IR-nature test.

No, this doesn't make sense, since RDF graphs are supposed to have "meaning".

Jonathan

>
> On May 10, 2010, at 10:52 AM, Jonathan Rees wrote:
>
>> I always have a hard time remembering whether an RDF graph is an
>> information resource or not, but the email from Ian Davis cited by the
>> following message gives evidence that it normatively isn't...  Now I
>> wonder whether the TAG and/or TimBL reviewed rdf-sparql-query and
>> concurred with this determination; I don't remember any review, and if
>> there was none this borders on being a squatting issue for the term
>> "information resource". Seems draconian to me to require separate URIs
>> for the document and the graph and weird to say that g in "graph { g }
>> ..." is not a graph. But what do I know.
>>
>> Jonathan
>>
>> ---------- Forwarded message ----------
>> From: Ian Davis <me@iandavis.com>
>> Date: Sat, May 8, 2010 at 5:48 AM
>> Subject: Re: [pedantic-web] Re: The OWL Ontology URI
>> To: pedantic-web@googlegroups.com
>>
>> On Fri, May 7, 2010 at 5:53 PM, Richard Cyganiak <richard@cyganiak.de>
>> wrote:
>>
>>> To put it another way: An N-Triples serialization of an RDF graph is a
>>> perfect representation of that graph. The fact that you can round-trip
>>> between them makes this clear. If it can have a representation, then it's
>>> an
>>> information resource and therefore it can be published as a web document
>>> (with 200 status code that returns the representation).
>>
>> Well I argued this way 2 years ago, but it's not the consensus and
>> it's at odds with e.g. cwm. See messages around
>> http://lists.w3.org/Archives/Public/www-tag/2008Jan/0071.html
>>
>>>> Most of the schemas in your second group were authored by me, or
>>>> by people advised by me, but I now believe they are wrong.
>>>
>>> Good to hear that. Any chance of getting these schemas changed, in the
>>> mid-term?
>>
>> I'll work on it.
>>
>> Ian
>>
>>
>
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Received on Tuesday, 11 May 2010 18:39:25 UTC

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