W3C home > Mailing lists > Public > public-rdf-wg@w3.org > February 2012

Re: Islands (ACTION-148)

From: Ivan Herman <ivan@w3.org>
Date: Tue, 28 Feb 2012 10:45:04 +0100
Cc: Andy Seaborne <andy.seaborne@epimorphics.com>, RDF-WG <public-rdf-wg@w3.org>
Message-Id: <DB1EF515-AACC-4FC3-B79D-F26EEC90FCF8@w3.org>
To: Pat Hayes <phayes@ihmc.us>
Pat,

I need explanation, 'cause I am lost, I am not ashamed to say that...


On Feb 27, 2012, at 22:42 , Pat Hayes wrote:
[snip]
> 
>> 
>> The use of a URI for a graph label in two different trig documents should mean the same thing but combining two datasets, like combining two graphs, will involve an application deciding that is can be done.
> 
> But how will it? ANY two graphs are semantically consistent, on this account,

If my understanding of [2] is correct, each graph must be, individually, consistent according to the RDF Semantics, ie, has to have a proper model. The models may be different for two different graphs with different labels, but I do not understand what you say...


> and two graphs (with different labels) NEVER entail any graph larger than either of them (such as their merge, for example), according to the semantics in [2].

Again, I do not understand why. If two graphs have the same label, then their merge, with the same label, is entailed, again by [2].

Ivan



> So all semantic relationships are reduced to triviality, so there can be no criteria available to check for acceptability on any semantic grounds. Remember, *every* URI might mean sometjhing completely different in another graph, so you can't say things like one graph says that x:joe is age 10 and the other says he is age 12: that URI might refer to Joe in one graph and Susan in the other, and the URI for the age property might mean age in one graph and being-a-handle-of in the other. Graphs become black holes of meaning, without any way for anything inside to influence or connect with anything outside. 
> 
>> 
>> Islands aren't named or formally recognized - and one apps view of "usable together" may not be the same as another apps.
> 
> Oh what a tangled Web we weave.... (Sorry, couldnt resist :-)
> 
> Pat
> 
>> 
>> 	Andy
>> 
>> [1] http://www.bbc.co.uk/doctorwho/dw
>> [2] http://www.w3.org/2011/rdf-wg/wiki/TF-Graphs/RDF-Datasets-Proposal
>> 
>> 
> 
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----
Ivan Herman, W3C Semantic Web Activity Lead
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Received on Tuesday, 28 February 2012 09:45:19 UTC

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