W3C home > Mailing lists > Public > public-lod@w3.org > July 2010

Re: RDF Extensibility

From: Pat Hayes <phayes@ihmc.us>
Date: Thu, 8 Jul 2010 12:16:06 -0500
Cc: Dan Brickley <danbri@danbri.org>, Linked Data community <public-lod@w3.org>, Semantic Web <semantic-web@w3.org>
Message-Id: <855DB070-B5B9-4BC6-AC83-F29F5C2F440A@ihmc.us>
To: Toby Inkster <tai@g5n.co.uk>

On Jul 7, 2010, at 6:57 AM, Toby Inkster wrote:

> On Tue, 6 Jul 2010 16:11:19 -0500
> Pat Hayes <phayes@ihmc.us> wrote:
>
>> The world doesn't have facts like that in it. Classes and properties
>> are intellectual constructs, not the stuff of reality. Hell, if a
>> particle can be a wave, then surely a class can be a property.
>> Anyway, RDF doesn't make logical a priori rulings about these kind
>> of metaphysical segregations. For example, xsd:Number is a class, a
>> property and an individual in RDF.
>
> Indeed - but who has claimed that classes and properties are disjoint?
> Although they may well overlap in some cases, foaf:Person still  
> isn't a
> property.
>
> Without knowing the definition of foaf:Person, it's difficult to
> conclude that foaf:Person is not a property. However, even without
> knowing the definition of a literal, it is easy to conclude that it is
> not a suitable node to be used as a property

Well, thats what I thought too, until people started using them that  
way in CLIF/IKL. It is very dangerous to presume that one can see  
clearly, ahead of time, that a construct cannot be usefully be used by  
anybody else. And such triples do have a meaning, technically, since  
the RDF semantics gives them one, without indeed any modification *at  
all*.

> , so in my opinion, it is
> sensible to state that triples containing a literal as the predicate
> have no meaning (even though I think they should be syntactically
> allowed).

I would veto this option. To do this would be a lot more work than not  
doing it; and it would greatly complicate the semantic specification,  
which would have to keep track of this 'meaninglessness'. One could  
have a situation, for example, in which A entails B entails C, A and C  
are perfectly fine, but B has been declared 'meaningless'. Should this  
inference be blocked? Should it be an error? Why are we even asking  
this question?

Pat

>
> -- 
> Toby A Inkster
> <mailto:mail@tobyinkster.co.uk>
> <http://tobyinkster.co.uk>
>
>

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Received on Thursday, 8 July 2010 17:17:36 UTC

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