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Re: What is it that's wrong with rdf:List

From: Pat Hayes <phayes@ihmc.us>
Date: Sun, 20 Jun 2010 10:05:23 -0500
Cc: Andy Seaborne <andy.seaborne@talis.com>, Paul Gearon <gearon@ieee.org>, Norman Gray <norman@astro.gla.ac.uk>, Semantic Web <semantic-web@w3.org>
Message-Id: <AF3A800A-6A97-4C31-BA91-11D45898946C@ihmc.us>
To: Alan Ruttenberg <alanruttenberg@gmail.com>

On Jun 20, 2010, at 8:32 AM, Alan Ruttenberg wrote:

> On Sat, Jun 19, 2010 at 5:05 PM, Pat Hayes <phayes@ihmc.us> wrote:
>>> As Paul says, update is not pretty.
>>>
>>> The complete solution would be to have lists as first class data  
>>> object in the RDF model (as well as bags).
>>
>> Um, they are. Lists as described by the RDF List vocabulary are  
>> *exactly* the LIsp model of a list.
>
> Nope. An RDF list doesn't constrain rdf:first to be single value. It
> doesn't constrain rdf:rest to be either a single rdf:list or rdf:nil.
> So you can make all sorts of structures using rdf lists that don't map
> to lisp lists.
>

Yes and no. RDF doesn't "make" anything, it describes things. Lists as  
described by RDF have exactly the structure of LISP S-expressions.  
However, just as with any other descriptive language, you can also say  
nonsense in RDF. In particular, you can say things using the list  
vocabulary that don't describe any actual lists, just as you can  
assert, once you have a property fatherOf, that someone is their own  
father.

My point to Andy was that what one might call the RDF List 'model' was  
quite conventional, and that SPARQL could simply assume that RDF list  
descriptions were correct and complete, and it would be acceptable for  
queries to fail when the RDF was list- crazy in the kind of way you  
describe.  But I apparently misunderstood his point, so this is now  
moot.

Pat


> -Alan
>

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Received on Sunday, 20 June 2010 15:07:43 GMT

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