Re: using classes to control constraints

I am still failing to see a sufficient distinction. Especially since, as
you say, languages where  a definition can be both a class and a shape are
possible and exist. I would also add desirable to possible.

<What would it mean to assert that an object belongs to a ShExC shape via an
rdf:type link?>

Why is this question relevant? We are not standardizing ShExC but creating
a new standard.

If you want to point out that there are some languages where classes and
shapes must be disjoint, I am sure it is possible to define such language
and ShExC may be an example of one. [I don't know if it is].

Irene

On Wed, Feb 11, 2015 at 11:40 AM, Peter F. Patel-Schneider <
pfpschneider@gmail.com> wrote:

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> In RDF (not RDFS) class membership can only be directly asserted, by means
> of rdf:type triples.  In RDFS you can assert class membership and via
> subclassing infer membership in other superclasses.  However, this all
> directly depends on asserting class membership via rdf:type triples.
>
> You never (at least as far as I can tell) assert membership in a shape.
> Instead a shape provides recognition conditions that precisely determine
> which nodes in a graph belong to the shape.  A shape implementation turns
> this determination into a procedural process.  You can then ask whether a
> node in a graph belongs to a shape.
>
> So, although shapes and RDF(S) classes are indeed related to sets, and one
> can talk about the members of a shape and the members of an RDF(S) class,
> there are distinct differences between the two.
>
>
> In some modelling languages there are constructs that are both classes and
> shapes.  For example, OWL descriptions work this way.  You can assert that
> an object belongs to a description and you can also recognize whether an
> object belongs to a description.  For many descriptions, this recognition
> process does not depend at all on any explicit typing assertions.
>
>
> What would it mean to assert that an object belongs to a ShExC shape via an
> rdf:type link?
>
>
> peter
>
>
> On 02/11/2015 08:09 AM, Irene Polikoff wrote:
> > Peter,
> >
> > Could you clarify this more? I don't see the contrast you are trying to
> > communicate and I am not sure what you mean by "recognized".
> >
> > Class membership is asserted. However, it can also be inferred which I
> > am interpreting the same as "recognized".
> >
> > I don't think membership in the shape is recognized if by "recognized"
> > you mean that there is some computational process that decides whether
> > something is a member of a shape or not. It is asserted in a sense that a
> > statement is made about the membership.
> >
> > In the end, however, they both have members.
> >
> > Irene
> >
> > On Wed, Feb 11, 2015 at 9:33 AM, Peter F. Patel-Schneider
> > <pfpschneider@gmail.com <mailto:pfpschneider@gmail.com>> wrote:
> >
> > Classes are things that you assert membership in.  Shapes are things
> > that you recognize membership in.
> >
> > I'm certainly open to other syntaxes.
> >
> > peter
> >
> >
> >
> > On 02/09/2015 09:19 PM, Holger Knublauch wrote:
> >> Hi Peter,
> >
> >> your email below seems to clarify how OWL Closed World would work. But
> >> I don't see a response to my questions at the end of my previous email
> >> in this thread (at the bottom here), especially on whether you would
> >> accept any other syntax than OWL at all.
> >
> >> Thanks, Holger
> >
> >
> >
> >
> >> On 2/8/2015 8:26, Peter F. Patel-Schneider wrote: In OWL constraints
> >> for RDF, OWL axioms are used as constraints.  However, this doesn't
> >> make RDF(S) classes be constraints.
> >
> >> You still create RDFS ontologies in the normal way, and constraints
> >> don't have a role to play there.  Or maybe you don't have an ontology
> >> at all.
> >
> >> It is only when you want to validate some data that the constraints
> >> play a role at all, and the constraints don't play the role of classes
> >> or even part of the description of a class.  You can have multiple
> >> constraint sets that employ classes from a particular ontology
> >> depending on just how your data needs to be.
> >
> >> Note in particular that if you need named shapes (a.k.a. closed world
> >> recognition) that these named shapes are only used for recognition,
> >> i.e., there are no type links that make individuals belong to these
> >> shapes.
> >
> >
> >> peter
> >
> >
> >
> >
> >> On 02/07/2015 01:35 PM, Holger Knublauch wrote:
> >>>>> On 2/8/15 12:44 AM, Peter F. Patel-Schneider wrote:
> >>>>>> I am very strongly in favour of having shapes be different
> >>>>>> from RDFS classes
> >>>>> Hi Peter, would you mind explaining your statement above? Your
> >>>>> original proposal to the WG was OWL Closed World, which
> >>>>> re-interprets restrictions with closed world meaning:
> >>>>>
> >>>>> ex:Class a owl:Class ; rdfs:subClassOf [ a owl:Restriction ;
> >>>>> owl:onProperty ex:property ; owl:minCardinality 1 ; ] .
> >>>>>
> >>>>> The equivalent in LDOM is:
> >>>>>
> >>>>> ex:Class a owl:Class ; ldom:property [ a ldom:PropertyConstraint
> >>>>> ; ldom:predicate ex:property ; ldom:minCount 1 ; ] .
> >>>>>
> >>>>> Where do these approaches differ? If you would not accept the
> >>>>> second syntax, do you have any other syntax than OWL that you
> >>>>> would accept?
> >>>>>
> >>>>> Thanks Holger
> >>>>>
> >>>>>
> >
> >
> >
> >
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