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Re: Subjects as Literals, [was Re: The Ordered List Ontology]

From: Pat Hayes <phayes@ihmc.us>
Date: Fri, 2 Jul 2010 00:41:21 -0500
Cc: Linked Data community <public-lod@w3.org>, Semantic Web <semantic-web@w3.org>
Message-Id: <340FAE5F-606B-4B93-A638-F8102DDD76C2@ihmc.us>
To: nathan@webr3.org

On Jul 2, 2010, at 12:07 AM, Nathan wrote:

> Pat Hayes wrote:
>> On Jul 1, 2010, at 11:49 PM, Nathan wrote:
>>> Pat Hayes wrote:
>>>> On Jul 1, 2010, at 11:18 AM, Yves Raimond wrote:
>>>>> "A literal may be the object of an RDF statement, but not the  
>>>>> subject
>>>>> or the predicate."
>>>> Just to clarify, this is a purely syntactic restriction. Allowing  
>>>> literals in subject position would require **no change at all**  
>>>> to the RDF semantics. (The non-normative inference rules for RDF  
>>>> and RDFS and D-entailment given in the semantics document would  
>>>> need revision, but they would then be simplified.)
>>> I have to wonder then, what can one all place in the s,p,o slots  
>>> without changing the RDF semantics? literal and bnode predicates  
>>> for instance? variables or formulae as in n3?
>>> read as: if a new serialization/syntax was defined for RDF what  
>>> are the limitations for the values of node/object and relationship  
>>> specified by the RDF Semantics?
>> None at all. The semantics as stated works fine with triples which  
>> have any kind of syntactic node in any position in any combination.  
>> The same basic semantic construction is used in ISO Common Logic,  
>> which allows complete syntactic freedom, so that the the same name  
>> can denote an individual, a property, a function and a proposition  
>> all at the same time.
>> Pat
>> PS. Its not a dumb question :-)
> thus is N3 valid RDF? (I read yes, but want/need to hear that's  
> right!)

Well, no. It depends what you mean by 'valid RDF'. N3 obviously has a  
lot of syntax that goes way beyond what is legal in RDF, so its not  
valid RDF. But if you mean, the basic RDF semantics can be extended to  
cover all the constructs in N3 (without completely breaking) then yes,  
it can. In fact, N3 is a subset of Common Logic, and the same basic  
semantic construction of RDF works for all of CL.  But it would be a  
real extension, in that all the 'extra' syntax of N3 (notably, the  
graph literals idea) would need to have its semantics specified  
explicitly. It wouldn't come for free.

Hope I've answered your question (?)


> ty so far,
> nathan

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Received on Friday, 2 July 2010 05:42:25 UTC

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