W3C home > Mailing lists > Public > semantic-web@w3.org > October 2007

Re: representing null in semantic frameworks

From: Alan Ruttenberg <alanruttenberg@gmail.com>
Date: Sat, 20 Oct 2007 19:37:22 -0400
Message-Id: <7D316312-4CA6-4523-A5B5-CA86AA459C6E@gmail.com>
Cc: Garret Wilson <garret@globalmentor.com>, Semantic Web <semantic-web@w3.org>
To: Story Henry <henry.story@bblfish.net>

rdf:nil is something, specifically the empty collection.

However, there is owl:Nothing, the empty class. If you say, for  
instance, that some property has allValuesFrom owl:Nothing, then it  
can't have any value. There is no thing which is rdf:type owl:Nothing.

-Alan

On Oct 20, 2007, at 12:25 PM, 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 Sunday, 21 October 2007 23:36:14 GMT

This archive was generated by hypermail 2.3.1 : Tuesday, 26 March 2013 21:45:18 GMT