- From: Dimitris Kontokostas <kontokostas@informatik.uni-leipzig.de>
- Date: Tue, 22 Nov 2016 00:11:21 +0100
- To: "Peter F. Patel-Schneider" <pfpschneider@gmail.com>
- Cc: "public-rdf-shapes@w3.org" <public-rdf-shapes@w3.org>
- Message-ID: <CA+u4+a0GBGPZhpFKiPSkOoMpxdXNXcVJ6skZN6oThA7yY-fgrQ@mail.gmail.com>
Thank you for your feedback Peter,
I updated the recursive shapes definition with your suggestions.
https://github.com/w3c/data-shapes/commit/1583bd6db8e1b08ecf1b3f747f7245486f4288cd
Best,
Dimitris
On Mon, Nov 21, 2016 at 3:58 PM, Peter F. Patel-Schneider <
pfpschneider@gmail.com> wrote:
> It does appear that now the only way for the validation of one shape to
> initiate validation of another shape is via the about six constraint
> components that take shapes as parameter values. This means no more filter
> shapes. It also means that there is no way that SPARQL-based SHACL
> constructs
> can initiate processing of another shape. This further means that the core
> SHACL constructs provide facilities that cannot be obtained through the
> SPARQL
> extension.
>
> In this considerably-changed SHACL the wording appears to be getting close
> to
> the intent of recursive shapes, i.e., that a recursive shape points back to
> itself via a chain of triples whose predicates are each sh:property or one
> of
> the shape-expecting constraint parameters. However, I do not think that
> the
> wording is yet adequate. Something along the following lines is required:
>
> "A shape *directly uses* another shape when that other shape is the value
> of a
> shape-expecting constraint parameter of the shape itself or one of the
> property constraints of the shape. The *uses* relationship between shapes
> is
> the transitive closure of the directly uses relationship. A shape is
> *recursive* if it uses itself."
>
> The handling of recursive shapes is also problematic as it appears that a
> SHACL processor is supposed to do something useful with recursive shapes.
> The
> wording should be expanded to allow SHACL processors to refuse to do
> anything
> with recursive shapes, i.e., by producing some sort of error during
> syntactic
> checking of shapes.
>
>
> Another problem with the current wording is that it permits parameters like
> sh:minCount to contribute to recursive shape determination.
>
> peter
>
>
> On 11/21/2016 02:10 AM, Dimitris Kontokostas wrote:
> > Dear Peter,
> >
> > Could you please check if you have further comments on the definition of
> > recursive shapes?
> > http://w3c.github.io/data-shapes/shacl/#shapes-recursion
> >
> > Best regards,
> > Dimitris
> >
> > On Tue, Sep 27, 2016 at 1:51 PM, Peter F. Patel-Schneider
> > <pfpschneider@gmail.com <mailto:pfpschneider@gmail.com>> wrote:
> >
> > I don't think that that the new wording is adequate.
> >
> > "A recursive shape is a shape thar refers to itself directly or
> transitively
> > via shape-based constraint components (i.e. sh:shape), logical
> constraint
> > components (i.e. sh:or), filter shapes (sh:filterShape) or the
> sh:hasShape
> > SPARQL function as defined in appendix A. The handling of recursive
> shapes is
> > not defined in SHACL and is left to SHACL processor implementations."
> >
> > s:s1 doesn't refer to itself. Instead, the validation of s:s1 on
> ex:foo5 ends
> > up having the determination of whether a violation should be reported
> > depending on whether a violation should be reported, even though
> there is no
> > path from s:s1 back to itself in the shapes graph. Different
> wording is
> > needed to describe this newly-detected problem with sh:hasShape.
> >
> > The wording also continues to not distinguish between
> >
> > ex:sr rdf:type sh:Shape ;
> > sh:class ex:c ;
> > sh:property [ rdf:type sh:ProperyConstraint;
> > sh:predicate ex:p ; sh:shape ex:sr ] .
> >
> > and
> >
> > ex:sr rdf:type sh:Shape ;
> > ex:class ex:c ;
> > rdfs:seeAlso [ rdf:type sh:ProperyConstraint;
> > sh:predicate ex:p ; sh:shape ex:sr ] .
> >
> >
> >
> > There needs to be a better definition of what counts as a recursive
> shape in
> > SHACL.
> >
> >
> > Peter F. Patel-Schneider
> > Nuance Communications
> >
> >
> >
> >
> > On 09/27/2016 12:44 AM, Dimitris Kontokostas wrote:
> > > As with other types of recursion, this is also unspecified in the
> spec
> > >
> > > I placed the sh:hasShape function in the recursive shape list
> > >
> > https://github.com/w3c/data-shapes/commit/
> 52396ff9014e055a6332c28516ac0574fb3c3211
> > <https://github.com/w3c/data-shapes/commit/
> 52396ff9014e055a6332c28516ac0574fb3c3211>
> > >
> > > On Mon, Sep 26, 2016 at 10:01 PM, Peter F. Patel-Schneider
> > > <pfpschneider@gmail.com <mailto:pfpschneider@gmail.com>
> > <mailto:pfpschneider@gmail.com <mailto:pfpschneider@gmail.com>>>
> wrote:
> > >
> > > What happens here? Why? Is what happens reasonable?
> > >
> > >
> > > Data graph
> > >
> > > @prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#
> > <http://www.w3.org/1999/02/22-rdf-syntax-ns#>
> > > <http://www.w3.org/1999/02/22-rdf-syntax-ns#
> > <http://www.w3.org/1999/02/22-rdf-syntax-ns#>>> .
> > > @prefix sh: <http://www.w3.org/ns/shacl#> .
> > > @prefix ex: <http://example.org/ex/> .
> > > @prefix s: <http://example.org/s/> .
> > >
> > > ex:foo1 rdf:type ex:foo ;
> > > rdf:type ex:bar ;
> > > s:shape s:bar .
> > >
> > > ex:foo2 rdf:type ex:foo ;
> > > rdf:type ex:baz ;
> > > s:shape s:bar .
> > >
> > > ex:foo3 rdf:type ex:foo ;
> > > rdf:type ex:baz ;
> > > s:shape s:baz .
> > >
> > > ex:foo4 rdf:type ex:foo ;
> > > rdf:type ex:baz ;
> > > s:shape s:s0 .
> > >
> > > ex:foo5 rdf:type ex:foo ;
> > > rdf:type ex:baz ;
> > > s:shape s:s1 .
> > >
> > > ex:foon1 rdf:type ex:foon ;
> > > rdf:type ex:baz ;
> > > s:shape s:s2 .
> > >
> > >
> > >
> > > Shapes graph
> > >
> > > @prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#
> > <http://www.w3.org/1999/02/22-rdf-syntax-ns#>
> > > <http://www.w3.org/1999/02/22-rdf-syntax-ns#
> > <http://www.w3.org/1999/02/22-rdf-syntax-ns#>>> .
> > > @prefix sh: <http://www.w3.org/ns/shacl#> .
> > > @prefix ex: <http://example.org/ex/> .
> > > @prefix s: <http://example.org/s/> .
> > >
> > > s:s1 rdf:type sh:Shape ;
> > > sh:targetClass ex:foo ;
> > > sh:sparql [
> > > sh:select
> > > """SELECT $this WHERE {
> > > $this s:shape ?shape ;
> > > BIND (sh:hasShape($this,?shape,$shapesGraph) AS
> ?hasShape)
> > > BIND (!bound(?hasShape) AS ?failure )
> > > FILTER (?failure || !?hasShape) }""" ] .
> > >
> > > s:bar sh:class ex:bar .
> > >
> > > s:baz sh:class ex:baz .
> > >
> > > s:s2 rdf:type sh:Shape ;
> > > sh:targetClass ex:foon ;
> > > sh:sparql [
> > > sh:select
> > > """SELECT $this WHERE {
> > > $this s:shape ?shape ;
> > > BIND (sh:hasShape($this,?shape,$shapesGraph) AS
> ?hasShape)
> > > BIND (!bound(?hasShape) AS ?failure )
> > > FILTER (?failure || ?hasShape) }""" ] .
> > >
> > >
> > > Peter F. Patel-Schneider
> > > Nuance Communications
> > >
> > >
> > >
> > >
> > > --
> > > Dimitris Kontokostas
> > > Department of Computer Science, University of Leipzig & DBpedia
> Association
> > > Projects: http://dbpedia.org, http://rdfunit.aksw.org,
> http://aligned-project.eu
> > > Homepage: http://aksw.org/DimitrisKontokostas <http://aksw.org/
> DimitrisKontokostas>
> > > Research Group: AKSW/KILT http://aksw.org/Groups/KILT
> > >
> >
> >
> >
> >
> > --
> > Dimitris Kontokostas
> > Department of Computer Science, University of Leipzig & DBpedia
> Association
> > Projects: http://dbpedia.org, http://rdfunit.aksw.org,
> http://aligned-project.eu
> > Homepage: http://aksw.org/DimitrisKontokostas
> > Research Group: AKSW/KILT http://aksw.org/Groups/KILT
> >
>
>
--
Dimitris Kontokostas
Department of Computer Science, University of Leipzig & DBpedia Association
Projects: http://dbpedia.org, http://rdfunit.aksw.org,
http://aligned-project.eu
Homepage: http://aksw.org/DimitrisKontokostas
Research Group: AKSW/KILT http://aksw.org/Groups/KILT
Received on Monday, 21 November 2016 23:12:23 UTC