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RE: representing null in semantic frameworks

From: Mark Cidade <marxidad@marxidad.com>
Date: Sat, 20 Oct 2007 15:00:35 -0400
To: "'Garret Wilson'" <garret@globalmentor.com>
Cc: "'Story Henry'" <henry.story@bblfish.net>, "'Semantic Web'" <semantic-web@w3.org>
Message-ID: <012b01c8134b$7fcff830$7f6fe890$@com>

What about owl:Nothing?

http://www.w3.org/TR/2004/REC-owl-guide-20040210/#owl_Nothing

Mark

-----Original Message-----
From: semantic-web-request@w3.org [mailto:semantic-web-request@w3.org] On
Behalf Of Garret Wilson
Sent: October 20, 2007 12:40 PM
To: Story Henry
Cc: Semantic Web
Subject: Re: representing null in semantic frameworks


Right. rdf:nil is an instance of rdf:List that is used to say something 
like, "the next list of this linked list is really no list at all" (i.e. 
L rdf:rest rdf:nil; see <http://www.w3.org/TR/rdf-schema/#ch_nil>).

So in other words RDF created a special null value that is only valid 
for use with rdf:List. Does anyone know of any meeting minutes or other 
documents that unveil why the WG didn't create a more general null that 
you could use for anything?

Thanks, Henry.

Garret

Story Henry wrote:
> There is something close. rdf:Lists terminate with a null I think.
>
> Henry
>
> On 20 Oct 2007, at 18:15, Garret Wilson wrote:
>
>>
>> As RDF evolved, was there any discussion on adding an rdf:null 
>> resource---that is, a resource that represents no resource at all?
>>
>> One expected response: "My child, you're thinking like a programmer 
>> again---what you really want to do is assert the absence of any 
>> assertions regarding a particular subject and predicate, or you want 
>> to assume a closed world and just don't assert anything at all", or 
>> something like that---and I appreciate this point of view to some 
>> extent.
>>
>> But as a practical matter, let's say we have a list of baseball game 
>> scores. Wouldn't it be convenient for the resource at index 3 to be 
>> null to indicate that there was no score that week because there was 
>> a tornado that canceled the game?
>>
>> I'm not necessarily looking for a big online discussion. Just a brief 
>> pointer to any reading on this subject would help. I'm sure there 
>> must have been some discussion of null over the development history 
>> of RDF.
>>
>> Thanks,
>>
>> Garret
>
Received on Saturday, 20 October 2007 19:01:22 GMT

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