Re: shapes-ISSUE-23 (punning): Shapes, classes and punning [SHACL Spec]

I would also prefer to have it separate with something like
ex:PersonShape
  a sh:Shape
  sh:onClass ex:Person
  sh:property [...]
.

But I also see why some people prefer the convenience to declare shapes
directly in a class. I am trying to understand the implications of punning
on the shape definitions and how a SHACL engine could differentiate between
class shapes and ShEx shapes.

Dimitris

On Fri, Apr 3, 2015 at 5:05 PM, Peter F. Patel-Schneider <
pfpschneider@gmail.com> wrote:

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> Punning was introduced in OWL 2 to allow for RDF graphs where IRIs are used
> as both classes and individuals.  At the time OWL 2 was designed it was not
> known whether it was possible to build effective OWL reasoners when
> inference about individuals (particularly equality) could affect the
> ontology (particularly implying that two classes are equal).
>
> I think that the idea for punning in SHACL is to allow for RDF nodes that
> denote both a shape and a class while still keeping these two identities
> apart.   In this way stating that the type of an individual is a
> class&shape
> would not trigger any shape-based stuff, because typing would be on the
> class identity, not the shape identity.
>
> I don't like using punning for this purpose.  For starters, I think that it
> will be hard to describe to users.  I much prefer a clean distinction
> between classes and conditions/constraints/shapes.
>
> peter
>
>
> On 04/02/2015 01:20 PM, Arthur Ryman wrote:
> > Richard,
> >
> > Thx. I believe that OWL needed to introduce punning because in strict
> > Description Logic there is a partitioning of resources into disjoint
> > sets, i.e. Class, Property, Individual.
> >
> > I don't believe that we are basing SHACL on DL. Therefore there is no
> > problem with SHACL triples having a their subject as a Class. Is there
> > some problem with this? What am I missing? Do you imagine that a SHACL
> > engine would need some way to distinguish a Shape from a Class? i.e.
> > given an IRI, if it's a Class to one thing else if it's a Shape do some
> > other thing?
> >
> > -- Arthur
> >
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-- 
Dimitris Kontokostas
Department of Computer Science, University of Leipzig
Research Group: http://aksw.org
Homepage:http://aksw.org/DimitrisKontokostas