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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 00:49:01 -0700
Message-ID: <53C8D16D.20503@gmail.com>
To: Jose Emilio Labra Gayo <jelabra@gmail.com>, Karen Coyle <kcoyle@kcoyle.net>
CC: "public-rdf-shapes@w3.org" <public-rdf-shapes@w3.org>
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.


On 07/17/2014 02:05 PM, Jose Emilio Labra Gayo wrote:
>     On 7/16/14, 9:38 PM, Holger Knublauch wrote:
>         Most people in my experience don't care about open world semantics, but
>         of course nobody would admit that because it's against the specs and
>         thousands of academic papers.
>     The cultural heritage community cares deeply about open world semantics.
>     This community has a tradition of creating primarily public-facing data
>     and, even in pre-Web eras, sharing that data widely. For the cultural
>     heritage community, the public, open web is the primary target for its data.
>     You confirm for me the impression that much of the discussion here is in
>     the context of enterprise data systems. I will, however, do my best to
>     keep the open world visible in these discussions.
> I don't think that those 2 visions (open & closed world) are incompatible. As
> Kendall Clark noticed, constraint checking can also be combined with Open
> World systems. One goal of Shape Expressions is to help in the integration of
> heterogeneous systems in an Open World.
> In fact, one of the first points in the discussion of ShEx was the possibility
> to declare open shapes instead of closed ones. The difference is that in a
> declaration like:
> <PersonShape> { foaf:name xsd:string }
> and with the triples:
> :john foaf:name "John" .
> :mary foaf:name "Mary";
>           foaf:mbox <mailto:mary@m.com <mailto:mary@m.com>> .
> a system with open shapes would assign both :john and :mary the shape
> <PersonShape> because both have :foaf:name, while a system with closed shapes
> would only assign :john that shape, because :mary has an extra triple.
> Eric's implementation employs Open shapes, while Shexcala first employed
> closed shapes and now admits both.
> In my opinion, closed shapes are good when you really need to ensure that your
> graph contains some triples and only those triples, while open shapes are
> better in an Open World where you want to ensure that your graph has some
> shape (if it has the triples declared in the shape) but it could also have
> some remaining triples.
> So as a general remark, I really think the cultural heritage domain can be a
> very nice use case where the needs of integrating data from different RDF data
> portals appear.
> Best regards, Jose Labra
>     kc
>     --
>     Karen Coyle
>     kcoyle@kcoyle.net <mailto:kcoyle@kcoyle.net> http://kcoyle.net
>     m: 1-510-435-8234 <tel:1-510-435-8234>
>     skype: kcoylenet
> --
> Saludos, Labra
Received on Friday, 18 July 2014 07:49:32 UTC

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