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Re: Action: #rdfms-identity-anon-resources questions

From: Graham Klyne <Graham.Klyne@Baltimore.com>
Date: Thu, 26 Jul 2001 20:27:02 +0100
Message-Id: <5.1.0.14.2.20010726202150.039ceae0@joy.songbird.com>
To: pat hayes <phayes@ai.uwf.edu>
Cc: w3c-rdfcore-wg@w3.org
Pat,

I think this discussion harks back to an earlier one, about creating a new 
language with core RDF as a subset (except, possibly, for some special 
properties that are not available for the normal interpretation).

I think this is probably getting out of scope for this forum, but I'd love 
to have a "corridor/bar discussion" with you about this in Stanford/Sebastopol.

#g
--

At 12:02 PM 7/26/01 -0700, pat hayes wrote:
>>At 10:15 PM 7/23/01 -0700, pat hayes wrote:
>>>It isnt clear to me what the scope of anonymous node is intended to be, 
>>>but it if it is the document containing the node, then indeed it should 
>>>be impossible for any other source to say anything about the thing it 
>>>refers to, so this is a genuine difference. However, the same is true of 
>>>a non-anonymous URI if its use is restricted to this one source.
>>
>>I've been thinking recently about encoding inference rules in RDF, where 
>>a rule may have a variable that is scoped by the rule; e.g.
>>
>>   Dog(?x) -> Animal(?x)
>
>OK, you have left me behind already. I don't see any way to get anything 
>remotely like that into RDF. I presume this is supposed to mean that for 
>any ?x, if it is a dog then it is an animal, right? How do we encode 
>universal quantifiers in an exist-conj logic like RDF?
>
>>Originally, I was thinking that, when encoding this in RDF the variable 
>>represented by ?x must somehow be scoped within the RDF. But when I 
>>started looking at candidate RDF encodings this need for scoping just 
>>melts away:  the variable is represented by a new, unique resource:
>
>??? Wait. Resources are the things in the world, the things that are 
>denoted by URI's, right? One doesnt get quantification by putting 
>variables into the *domain* (whatever that means: I'm not sure what it 
>means, to be honest. )
>
>>that resource has global scope (and, hence, if it has a URI it is one 
>>that is not shared by any other resource).  The only place where the 
>>concept of scope is needed is in the original expression.  Some other 
>>expression; e.g.
>>
>>   Cat(?x) -> Animal(?x)
>>
>>Has a different scope for its ?x, but the resource that represents the 
>>variable in the encoding of this is a different resource than the one 
>>that represents ?x in the previous example.
> From this exercise, I tentatively suggest that the scope of any
>>resource (node) is global -- the entire universe of discourse.
>
>Well, I think I follow your point, and indeed one can do something like 
>this in conventional logic, where its often called 'standardizing apart', 
>ie no variable name is ever used twice, so there is no risk of getting 
>them confused. But (1) it is unworkable in practice, and (2) you still 
>need some way to indicate, or determine, the scopes. For example, consider 
>the difference between
>foo & (cat(?x) -> animal(?x) )
>and
>(foo & cat(?x)) -> animal(?x)
>
>>(I'm trying to be clear that this is an encoding of inference rules in 
>>RDF, not an attempt to make inference rules part of RDF.)
>
>Maybe this is my problem. I'm not sure what this distinction amounts to. 
>RDF has a 'meaning' already, so how does one get its meaning changed so it 
>can do this encoding for you?
>
>Pat Hayes
>
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Graham Klyne                    Baltimore Technologies
Strategic Research              Content Security Group
<Graham.Klyne@Baltimore.com>    <http://www.mimesweeper.com>
                                 <http://www.baltimore.com>
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Received on Thursday, 26 July 2001 15:33:47 EDT

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