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Re: [TF-PP] cycles - simple or a walk

From: Ivan Herman <ivan@w3.org>
Date: Fri, 05 Mar 2010 09:05:21 +0100
Message-ID: <4B90BB41.9070109@w3.org>
To: Andy Seaborne <andy.seaborne@talis.com>
CC: SPARQL Working Group <public-rdf-dawg@w3.org>


On 2010-3-4 15:47 , Andy Seaborne wrote:
> 
> In
> http://lists.w3.org/Archives/Public/public-rdf-dawg-comments/2010Feb/0012.html
> 
> 
> Jeremy Carroll raises the issue of cycles.
> 
> Given:
> 
> eg:a eg:p eg:a
> eg:a eg:p eg:b
> 
> does "?a eg:p {3, 7} ?b" match ?b to both eg:a and eg:b by going round
> the loop in eg:a ex:p eg:a a few times.
> 
> One possibility is to allow this.

I would agree with that. After all, looking at the data, I would expect

SELECT ?x ?y WHERE {?x eg:p ?y.}

does return ?x/eg:a ?y/ex:a as possible answer, doesn't it? If on the
other hand, ?a eg:p {3, 7} ?b would not match ex:a for ?b that would be
in contradiction...

Ivan

> 
> The other is to spec that this does not contribute to the length of the
> path.  A "simple path" in the graph theory terminology.
> 
> http://en.wikipedia.org/wiki/Path_%28graph_theory%29
> 
>     Andy
> 

-- 

Ivan Herman, W3C Semantic Web Activity Lead
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Received on Friday, 5 March 2010 08:05:10 GMT

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