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Re: comments on SHACL Core Abstract Syntax and Semantics

From: Martynas Jusevičius <martynas@graphity.org>
Date: Sun, 28 Aug 2016 22:49:51 +0200
Message-ID: <CAE35VmwRLak-eS7z2zichW4Fp3n6aXb+MD+shTDUkkCYhZ1RWg@mail.gmail.com>
To: "Peter F. Patel-Schneider" <pfpschneider@gmail.com>
Cc: Karen Coyle <kcoyle@kcoyle.net>, public-rdf-shapes@w3.org, James Anderson <james@dydra.com>
I am wondering about the notation:
https://www.w3.org/TR/shacl-abstract-syntax/#notation

Is this some notation created specifically for this document? Or this
some standard/common notation reused? If not, why not?

I am working on a specification that attempts to define semantics for
SPARQL-backed Linked Data, so it would be good to know. Currently we
use denotational semantics:
https://en.wikipedia.org/wiki/Denotational_semantics

On Sat, Aug 27, 2016 at 8:55 PM, Peter F. Patel-Schneider
<pfpschneider@gmail.com> wrote:
> Yes I mean the English language descriptions of the meanings of the various
> constructs.   This provides a semantics for SHACL, albeit an informal one.
>
> Examples of syntax are examples of syntax, i.e., not semantic.  Providing an
> informal description of these examples is semantics of a sort, but saying what
> an example means is generally considered to not to have any normative force.
>
> peter
>
>
> On 08/27/2016 08:46 AM, Karen Coyle wrote:
>> Thank you, Peter, these are great comments. We'll incorporate as many as we
>> can into the next version of the document.
>>
>> I do have a question about your use of the term "semantics" because it may be
>> different from mine. By "semantics" do you mean the English-language
>> explanations of the syntax? And if so, does that also include the examples?
>>
>> Thanks again,
>> kc
>>
>> On 8/26/16 11:09 AM, Peter F. Patel-Schneider wrote:
>>> 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 Sunday, 28 August 2016 20:50:20 UTC

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