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Re: SHACL recursion based on SPARQL (idea)

From: Dimitris Kontokostas <kontokostas@informatik.uni-leipzig.de>
Date: Thu, 3 Mar 2016 20:36:48 +0100
Message-ID: <CA+u4+a3vanqJVAkfZSCkX7NEV8FJovvCbG8pALaL7KYe--+Zzg@mail.gmail.com>
To: "Peter F. Patel-Schneider" <pfpschneider@gmail.com>
Cc: public-data-shapes-wg <public-data-shapes-wg@w3.org>
On Thu, Mar 3, 2016 at 8:17 PM, Peter F. Patel-Schneider <
pfpschneider@gmail.com> wrote:

> It looks to me as if this is a way to determine what to run the shapes on
> in a
> bottom-up implementation.  However, it does not appear to address how to
> determine results when recursion happens, at least as far as I can see, and
> that is the issue that needs to be addressed for SHACL in general.
>
> For example, how does this approach address whether there is a violation in
>
> ex:a rdf:type ex:Person ;
>      p1 ex:o1 .
> ex:o1 p2 ex:o2 .
> ex:o2 p3 ex:o3 .
> ex:o3 p1 ex:o1 .
>

My idea was to rely on SPARQL on this, the same way we define the rest of
shacl in SPARQL. We can test what SPARQL returns on edge cases like this
and rely on that.


>
> peter
>
> On 03/02/2016 11:54 PM, Dimitris Kontokostas wrote:
> > I maybe surprising to the group that I make such a proposal :) but had a
> > (crazy) idea about enabling *some* recursion on shacl that is consistent
> with
> > the rest of the spec and is based in SPARQL.
> >
> > The basic idea is to use implicit scopes and property paths to achieve
> that goal.
> > (Note that I have not yet implemented this, this is just a draft idea and
> > wanted to see if you would like to explore more on this)
> >
> > Example:
> > ShpA (scopeClass ex:Person, property(p1, valueShape: ShpB))
> > ShpB ( property (p2, isIRI, (valueShape: ShpC))
> > ShpC ( property (p3, isIRI, (valueShape: ShpA))
> >
> > In this approach, every shape may have an explicit scope (such as
> scopeClass,
> > scopeNode, etc) as well as implicit scopes that derive from sh:valuShape.
> > to identify the implicit scope of a shape we traverse all the current
> shape
> > references to that shape from other shapes and give them implicit scopes
> only
> > if the other shapes have an explicit scope.
> > An example with make it easier to understand
> >
> > (note that this is without recursion and is  how RDFUnit has currently
> > implemented sh:valueShape)
> > ShpA has an explicit scope with scopeClass ex:Person (we do not take
> ShpC into
> > account here)
> > ShpB has no explicit scope and 1 implicit scope: [a ex:Person] / p1
> > ShpC has no explicit scope and 1 implicit scope: [a ex:Person] / p1 / p2
> >
> > note that ShpC gets an implicit scope from ShpA only as ShpB has no
> explicit
> > scope, if it did, we would add an extra scope
> > to put this in SPARQL, ShpC would have the following scope
> > select ?this where { [] a ex:Person ; p1/p2 ?this }
> >
> > if we want to add recursion into this what we could do is something like
> the
> > following
> > ShpA has an explicit scope with scopeClass [ a ex:Person]  and 1 implicit
> > scope [a ex:Person] / (p1 / p2 / p3 )+
> > ShpB has no explicit scope and 1 implicit scope: [a ex:Person] / (p1 /
> p2 / p3
> > )* / p1
> > ShpC has no explicit scope and 1 implicit scope: [a ex:Person] / (p1 /
> p2 / p3
> > )* / p1 / p2
> >
> > As I said, this is just a draft idea for very simple recursion in simple
> shape
> > definitions.
> > I have not yet tested it or thought how this will behave in nested AND /
> OR (I
> > think NOT is out of the question anyway), I just wanted to share this
> and get
> > you feedback if it is worth exploring more
> >
> > Best
> > Dimitris
> >
> >
> > --
> > Dimitris Kontokostas
> > Department of Computer Science, University of Leipzig & DBpedia
> Association
> > Projects: http://dbpedia.org, http://rdfunit.aksw.org,
> > http://http://aligned-project.eu <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://
http://aligned-project.eu
Homepage:http://aksw.org/DimitrisKontokostas
Research Group: AKSW/KILT http://aksw.org/Groups/KILT
Received on Thursday, 3 March 2016 19:37:46 UTC

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