- From: Benja Fallenstein <b.fallenstein@gmx.de>
- Date: Wed, 17 Sep 2003 01:36:25 +0300
- To: Garret Wilson <garret@globalmentor.com>
- Cc: Dan Brickley <danbri@w3.org>, Art.Barstow@nokia.com, www-rdf-interest@w3.org
Garret Wilson wrote:
>
>
> Dan Brickley wrote:
>
>> * Art.Barstow@nokia.com <Art.Barstow@nokia.com> [2003-09-15 11:49-0400]
>>
>>> Do the latest RDF specs define a way to do enumeration
>>> (e.g. a Bag may contain only 4 strings)? If so, please
>>> send me the pointer.
>>
>>
>>
>> http://www.w3.org/TR/rdf-schema/#ch_collectionvocab
>> The rdf:List collections mechanism allows the members of a list to be
>> enumeated in a way that makes it clear the whole list has been
>> represented.
>
>
> But as one can always add an infinite number of rdf:first properties to
> any rdf:List resource (see your citation about), does this really help
> ensure that nothing more is added to a list---or even, as you put it,
> "makes it clear the whole list has been represented?"
While the RDF semantics do not define this (because they don't deal in
cardinalities), it is sensible to interpret rdf:first and rdf:rest to
have a cardinality of one. (I don't know whether OWL actually specifies
this.)
If you assume this, then given two triples,
foo:xxx rdf:first foo:abc
foo:xxx rdf:first foo:def
you can conclude that foo:abc and foo:def are the same thing, because a
list can have only one first element.
If you *know* that foo:abc and foo:def aren't the same (e.g. through
owl:differentIndividualFrom, or what it was), then you have arrived at a
contradiction.
I.e., with rdf:List, you know that there cannot be additional rdf:first
or rdf:rest triples "somewhere out there" that change the elements of
the list. If there are additional rdf:first triples, then either there
are two different nodes for the same resource, or someone has stated a
contradiction.
Cheers,
- Benja
Received on Tuesday, 16 September 2003 18:38:49 UTC