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Re: summary so far.

From: Jonathan Rees <jar@creativecommons.org>
Date: Wed, 2 Mar 2011 14:03:06 -0500
Message-ID: <AANLkTimc01x68LMFsVcDPThv1zY7hh2CHrNWtiiqV+SJ@mail.gmail.com>
To: nathan@webr3.org
Cc: Pat Hayes <phayes@ihmc.us>, AWWSW TF <public-awwsw@w3.org>
On Wed, Mar 2, 2011 at 1:40 PM, Nathan <nathan@webr3.org> wrote:
> Pat Hayes wrote:
>>
>> On Mar 2, 2011, at 11:30 AM, Nathan wrote:
>>
>>> Jonathan Rees wrote:
>>>>
>>>> You're generting stuff more quickly than I can process it. I will be
>>>> selective and not comment on everything that I could.
>>>
>>> np, feedback, or a call to discuss, the last iteration:
>>>  http://lists.w3.org/Archives/Public/public-awwsw/2011Mar/0014.html
>>> would be appreciated, and how it maps out to, or affects ir-axioms.
>>>
>>>> On Wed, Mar 2, 2011 at 5:49 AM, Nathan <nathan@webr3.org> wrote:
>>>>>
>>>>> Jonathan Rees wrote:
>>>>> now this is interesting, and I'm unsure exactly how to say it, but if
>>>>> we
>>>>> work from HTTP Resource upwards to URI, such that we consider an HTTP
>>>>> Resource as being a distinct object for which all URIs used to refer to
>>>>> it
>>>>> are bound to that HTTP Resource (the URIs are a property of the HTTP
>>>>> Resource), then we come to the wrong conclusions, and things break.
>>>>
>>>> No. Only TimBL's requirement that these be distinct breaks. (Maybe
>>>> that's what you mean by "things" but you need to be more specific.)
>>>
>>> and RDF's requirement, in fact URIs is it not, that two different URIs
>>> refer to two different things unless explicitly stated that they refer to
>>> the same thing?
>>
>> No. RDF (and RDFS, OWL etc.) make no assumptions about unique naming. Any
>> two different URIs might or might not refer to the same thing.
>
> surely there is some world view, that given <x> and <y>, unless you know,
> infer, or are told otherwise, then they refer to different things? or is the
> view that given any two URIs it is default to consider them as all referring
> to the same thing?

You have to go back to the model theory to understand this properly.
The following leaves a few details out, but its sloppiness shouldn't
detract from the point.

Suppose you have a graph that contains no logical connectives
(subclassof etc.). Then it has many (RDF) interpretations, at least
one in which every URI is interpreted as a distinct individual or
property, and one in which every URI is interpreted as the same
individual or property.

That is, if there are no axioms to tell you, then you just don't know
what's the same and what's not - the theory of the graph is logically
incomplete in this regard. The only way an equality or inequality
would be 'known' is if it were entailed - i.e. true in every
interpretation.

Hope that helps.

> take for example the case in question:
>  http://lists.w3.org/Archives/Public/public-awwsw/2011Mar/0006.html
>
> by looking only at the set of representations only, you'd conclude that they
> are all the same (?), by looking at the URIs only, you'd conclude that they
> are different (?)

To have HTTP feed into an RDF graph you'd have to have specify some
process doing the translation, with HTTP exchanges as input and RDF
graphs (axioms) as output. This is sort of implicit in the webarch
theory but has never been codified really. That process was a chunk of
the work we did in AWWSW a year or two ago, but it's been put aside
for now.

Jonathan

> what's your view on this case, how do you think/feel it should be
> (personally).
>
> Best,
>
> Nathan
>
Received on Wednesday, 2 March 2011 19:03:38 GMT

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