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Re: is there an implementation of Shape Expressions that correctly handles recursive shapes?

From: Peter F. Patel-Schneider <pfpschneider@gmail.com>
Date: Wed, 25 Mar 2015 06:34:25 -0700
Message-ID: <5512B961.7050104@gmail.com>
To: Eric Prud'hommeaux <eric@w3.org>
CC: RDF Data Shapes Working Group <public-data-shapes-wg@w3.org>
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I think that the Fancy Shape Expressions demo at
www.w3.org/2013/ShEx/FancyShExDemo doesn't accurately implement the
axiomatic semantics. (It's a bit hard to tell, though, because the
axiomatic semantics is rather complicated.)

What I am seeing is that in

PREFIX ex: <http://ex.example/#>
start = <S>
<S> { ex:p1 @<T> , ex:p2 @<T> }
<T> { ( ex:q @<Z> | ex:r @<T> ) }
<Z> { }

PREFIX ex: <http://ex.example/#>
ex:a ex:p1 ex:b .
ex:a ex:p2 ex:c .
ex:b ex:q ex:z .
ex:c ex:q ex:z .
ex:b ex:r ex:c .
ex:c ex:r ex:b .

ex:a doesn't validate against <S>.

In the axiomatization, however, the two conjuncts for <S> have independent
context extensions (at least as far as I can tell), and so permit different
"interpretations" of the loop, which allows both ex:b and ex:c to be
validated as <T>.

peter
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Received on Wednesday, 25 March 2015 13:35:15 UTC

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