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Re: [TF-PP] Property Path FPWD

From: Ivan Herman <ivan@w3.org>
Date: Mon, 04 Jan 2010 18:56:06 +0100
Message-ID: <4B422BB6.2010306@w3.org>
To: Andy Seaborne <andy.seaborne@talis.com>
CC: Souripriya Das <SOURIPRIYA.DAS@oracle.com>, Lee Feigenbaum <lee@thefigtrees.net>, Axel Polleres <axel.polleres@deri.org>, W3C SPARQL Working Group <public-rdf-dawg@w3.org>
You win:-)

Yes, you are right. Keep it that way. Maybe adding these
explanations/examples may help others, too...

Cheers

Ivan

On 2010-1-4 17:53 , Andy Seaborne wrote:
> 
> 
> On 04/01/2010 12:31 PM, Ivan Herman wrote:
>> Hi Andy,
>>>> - I am not sure what "A path of length zero connects a graph node to
>>>> itself." means in terms of a triple pattern...
>>>
>>> ?x :p* ?y needs a meaning.  :p* can appear in more complex paths
>>> (rdf:first*/rdf:rest).
>>>
>>> Working backwards from e.g. ?list rdf:first*/rdf:rest ?elt, ?list
>>> rdf:first* ?x would match with ?x equal to whatever ?list is.
>>>
>>
>> Hm. Alternatively, ?x :p* ?y would not match anything with length zero?
> 
> Then ?list rdf:rest* ?elt does not match the beginning cell of a list and
> 
>   ?list rdf:rest*/rdf:first ?elt
> 
> (which eventually I will write correctly!)
> 
> does not find the first element of a list without making :p* different
> from the :p* in :p*/:q
> 
> It does have a nice effect that
> 
>   :C rdfs:subClassOf ?class
> 
> includes :C (as per inference rule that :C rdfs:subClassOf :C).
> 
> An app can write "+" to skip the zero match "+" is '1 or more' where "*"
> is 'zero or more'
> 
>     Andy
> 

-- 

Ivan Herman, W3C Semantic Web Activity Lead
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Received on Monday, 4 January 2010 17:55:59 GMT

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