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Re: Formal objection to removing features from node shapes

From: Irene Polikoff <irene@topquadrant.com>
Date: Fri, 24 Feb 2017 22:17:09 -0500
Cc: "public-rdf-shapes@w3.org" <public-rdf-shapes@w3.org>
Message-Id: <9B7A45C2-3FAE-4BC5-92BF-EC84227EE101@topquadrant.com>
To: "Peter F. Patel-Schneider" <pfpschneider@gmail.com>
Peter,

Do you have examples of the loss of expressive power in cases of sh:minCount, sh:maxCount, sh:uniqueLang, sh:lessThan, sh:lessThanOrEquals, or sh:qualifiedValueShape constraint component?

Regards,

Irene


> On Feb 24, 2017, at 9:57 PM, Peter F. Patel-Schneider <pfpschneider@gmail.com> wrote:
> 
> This is a formal objection to the decision of the RDF Data Shapes working
> group to reclose ISSUE-139 by making node shapes ill-formed if they use any
> of sh:minCount, sh:maxCount, sh:uniqueLang, sh:equals, sh:disjoint,
> sh:lessThan, sh:lessThanOrEquals, or sh:qualifiedValueShape.
> 
> Node shapes that use any of these properties have suitable obvious
> definitions so there is no problem adding them back to SHACL.
> 
> With the resolution node shapes and property shapes have different features.
> This difference complicates the language, making it harder to explain to
> users and harder to machine-generate.  Because the language is more complex
> implementations become more complex and testing becomes more complex.
> 
> Removing these node shapes from the language causes a decided drop in
> expressive power.  For example,
> 
> ex:s1 rdf:type sh:NodeShape ;
> sh:targetClass ex:C1 ;
> sh:disjoint ex:p1 .
> 
> checks that SHACL instances of ex:C1 do not have themselves as a value for
> ex:p1.   This useful ability cannot be obtained through any other means.
> 
> So the resolution to close ISSUE-139 removes useful expressive power from
> SHACL without appreciably reducing implementation or testing costs or
> reducing user confusion.  All these features need to be added back to node
> shapes.
> 
> Peter F. Patel-Schneider
> Nuance Communications
> 
Received on Saturday, 25 February 2017 03:17:44 UTC

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