Re: rdfdatashapestracker-ISSUE-3 (Shape association): How is a shape associated with a graph?

* Holger Knublauch <holger@topquadrant.com> [2014-12-03 10:53+1000]
> If I understand the ticket's purpose correctly, then there are two
> dimensions
> 
> a) how to store, reference and share constraint definitions in
> graphs (Peter addressed that)
> b) how to instruct an engine so that it knows which checks to perform
> 
> On b) I believe there is a wide agreement that associating "shapes"
> with classes makes a lot of sense, and I believe all proposed
> mechanisms have some vocabulary for that purpose (in SPIN and OWL
> this is simply relying on the rdf:type arcs). At the same time,
> there are use cases where this association with classes is not the
> only mechanism, and some resources need to be checked against
> additional patterns in specific contexts. In Resource Shapes 2.0
> this is done (among others) via oslc:valueShape, and it sounds
> straight-forward to define similar properties that can be submitted
> as part of a constraint checking request. Resource Shapes 2.0 seems
> to have oslc:instanceShape and oslc:resourceShape for that purpose.
> I believe oslc:instanceShape is similar to rdf:type.

[[
The oslc:instanceShape property is used to link any described resource
with a shape resource that describes its contents.
]] — http://www.w3.org/Submission/2014/SUBM-shapes-20140211/#instanceShape

suggests to me that it connects an instance node to a shape, rather
than a type to a shape. I propose we use the predicate
shapes:typeShape until something better comes along.


> oslc:resourceShape seems rather specific to the web service
> architecture, and I am not sure how far the WG will reach in this
> regard. I would argue the latter could be an OSLC specific extension
> because it relies on concepts outside of our focus.
> 
> At this stage I am not sure what is missing to resolve this ticket.
> The ticket is about collecting all ways a shape can be associated
> with a graph. Peter has enumerated some. I have written that the
> rdf:type triples can be used. Who can elaborate on the other
> mechanisms employed by ShEx and Resource Shapes, and clarify which
> ones are proposed to be handled by the WG?

For ShEx, we use command line arguments to say "validate node <N> in
datatype <D> as shape <S>" and "find all shapes for every node in
dataset <D>".  See <https://github.com/labra/ShExcala/wiki> for an
example.

If we want properties for this, we can concoct something like
shapes:startingNode and shapes:startingShape for the former case. For
the latter, a schema is basically a closed set of shapes so we could
enumerate shapes to check but maybe it's more reasonable to point to
the schema.


> Thanks,
> Holger
> 
> 
> On 12/3/2014 5:58, Peter F. Patel-Schneider wrote:
> >On 11/18/2014 09:17 AM, RDF Data Shapes Working Group Issue
> >Tracker wrote:
> >>rdfdatashapestracker-ISSUE-3 (Shape association): How is a shape
> >>associated with a graph?
> >>
> >>http://www.w3.org/2014/data-shapes/track/issues/3
> >>
> >>Raised by: Arnaud Le Hors
> >>On product:
> >>
> >>There has been quite a bit of discussion about how a shape is
> >>associated with an instance graph. Some technologies rely on a
> >>type but this isn't accepted by all as sufficient to address all
> >>use cases. So, what are the ways a shape can be associated with
> >>a graph?
> >
> >
> >As far as I can see there are only a few potential mechanisms for
> >associating some constraints with an RDF graph.  (This is separate
> >from determining which part of the RDF graph the constraint acts
> >on, by the way.)
> >
> >1/ The constraint could be in the graph itself.
> >
> >2/ There could be an explicit connection between the graph and a
> >source for the constraint.  This would work something like
> >owl:imports, but the source would not have to be an ontology
> >document.  The connection could also be indirect, e.g., the graph
> >owl:imports an ontology document which is itself explicitly
> >connected to a constraint document.
> >
> >3/ There could be an implicit connection between the graph and a
> >source for the constraint.  This could be something like "follow
> >your nose", i.e., the graph has a node whose IRI can be turned
> >into a URL that points at a source for the constraint.  This
> >connection could also be indirect.
> >
> >4/ The constraint validation mechanism could take multiple
> >arguments, one of which is an RDF graph and another of which
> >contains constraints.  In this mechanism, as opposed to the other
> >three, there is no way of navigating from the RDF graph to the
> >constraint.
> >
> >
> >Some proposals naturally or easily work with several of the above
> >mechanisms.
> >
> >
> >peter
> >
> >
> 
> 

-- 
-ericP

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Received on Wednesday, 3 December 2014 22:18:23 UTC