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Re: Shapes/ShEx or the worrying issue of yet another syntax and lack of validated vision.

From: Peter F. Patel-Schneider <pfpschneider@gmail.com>
Date: Fri, 18 Jul 2014 02:01:21 -0700
Message-ID: <53C8E261.1030601@gmail.com>
To: Jose Emilio Labra Gayo <jelabra@gmail.com>
CC: Karen Coyle <kcoyle@kcoyle.net>, "public-rdf-shapes@w3.org" <public-rdf-shapes@w3.org>


On 07/18/2014 01:28 AM, Jose Emilio Labra Gayo wrote:
>              So you are saying that ShEx is ambiguous as to whether open or closed
>              semantics is to be applied?  That seems to be a problem with the ShEx
>              definition.
>
>
>         No, I am saying that there are two ways to implement Shape
>         expressions...one
>         with the open shapes that allows remaining triples and one with closed
>         shapes
>         which disallows them.
>
>
>     That's what I said, I think.
>
>
> Well, you asked if ShEx "is ambiguous as to whether open or closed semantics
> is to be applied?" and I answered no. Because it is not ambiguous with regards
> to open or closed semantcs. It just can handle open shapes or closed shapes.
>
> In fact, what I propose is a syntax for ShEx so a user can declare an open
> shape or a closed shape, which in my opinion is the best solution and is
> similar to what regular expressions offer.
>
> Best regards, Jose Labra


The ShEx definition provides a specification for evaluating shape expressions. 
  I was expecting that this would tell me what the result of evaluating a ShEx 
schema against an RDF graph is (perhaps with a particular starting point).

So, for example, I was expecting to be able to look at the definition and 
determine whether

<Sh> { ex:foo (ex:bar) }

validates the RDF graph below, starting with ex:w

ex:w ex:foo ex:bar .
ex:w ex:new ex:junk .

But you are telling me that that is not the case.  You are saying that the 
result here can be either pass or fail.  If true, that's an ambiguity in the 
ShEx definition.

peter
Received on Friday, 18 July 2014 09:01:54 UTC

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