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comments on SHACL Core Abstract Syntax and Semantics

From: Peter F. Patel-Schneider <peter.patel-schneider@nuance.com>
Date: Fri, 26 Aug 2016 11:09:33 -0700
To: <public-rdf-shapes@w3.org>
Message-ID: <81ac978c-fa03-1b3b-ba22-ffa05b7fdb8d@nuance.com>
Some comments on SHACL Core Abstract Syntax and Semantics first public
working draft 25 August 2016 at https://www.w3.org/TR/shacl-abstract-syntax/

There is a discrepancy between the title and abstract of the document.  The
title includes semantics but the abstract only talks about syntax.  The
document should be clear at the beginning about what it covers.

The body of the document does talk about the semantics of SHACL.  There is
already a semantics provided for SHACL in https://www.w3.org/TR/shacl/.
There does not appear to be any reason to have two different documents that
provide a semantics for SHACL, even with one of them being non-normative.
As there is no reason for a second version of the semantics of SHACL it
needs to be removed from this document.

The document appears to provide an abstract syntax for SHACL.  The abstract
and title say "core SHACL" but there is no discussion in the body of the
document as to just what is being covered.  If the document is just covering
the core of SHACL it needs to qualify what it is doing throughout the body
of the document.

The document does not even cover all of the core of SHACL.  For example, it
does not provide for severities or any of the non-validating aspects of
SHACL shapes.  This needs to be remedied or explained.

The document uses "SHACL instance graph".  This is probably referring to a
shapes graph and thus probably needs to be changed.  Instance graphs,
however, contain schemas, which are not defined for SHACL.

The document uses RDF Semantics as its source of definitions for some RDF
notation.  It would be better to reference RDF 1.1 Concepts and Abstract
Syntax where possible.

I think that the document in its current form has negative utility.  The
abstract syntax does not correspond to any coherent part of SHCL.  The
semantics is just going to be a competitor to the informal and formal
semantics in https://www.w3.org/TR/shacl/.  If the semantics stuff was
removed and the abstract syntax actually corrsponded to the SHACL core
syntax then there might be some small utility for the document.

Peter F. Patel-Schneider
Nuance Communications
Received on Friday, 26 August 2016 18:10:05 UTC

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