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Re: SHACL syntax and metamodel complexity

From: Arnaud Le Hors <lehors@us.ibm.com>
Date: Thu, 3 Mar 2016 15:22:23 -0800
Message-Id: <201603032322.u23NMVr7020251@d03av04.boulder.ibm.com>
To: "Peter F. Patel-Schneider" <pfpschneider@gmail.com>
Cc: public-data-shapes-wg@w3.org
Ah ok, I found where the restriction comes from in the spec:

http://w3c.github.io/data-shapes/shacl/#constraints-property

Section 3.1 Property Constraints (sh:property)
"None of these properties can be repeated within the same 
sh:PropertyConstraint. In order to define multiple constraints using the 
same property, such as multiple sh:hasValue constraints, the shape must 
use multiple sh:property definitions."

Thanks.
--
Arnaud  Le Hors - Senior Technical Staff Member, Open Web Technologies - 
IBM Software Group


"Peter F. Patel-Schneider" <pfpschneider@gmail.com> wrote on 03/03/2016 
02:45:54 PM:

> From: "Peter F. Patel-Schneider" <pfpschneider@gmail.com>
> To: Arnaud Le Hors/Cupertino/IBM@IBMUS
> Cc: kcoyle@kcoyle.net, public-data-shapes-wg@w3.org
> Date: 03/03/2016 02:46 PM
> Subject: Re: SHACL syntax and metamodel complexity
> 
> On 03/03/2016 01:42 PM, Arnaud Le Hors wrote:
> > "Peter F. Patel-Schneider" <pfpschneider@gmail.com> wrote on 
03/03/2016
> > 12:14:55 PM:
> > 
> >> From: "Peter F. Patel-Schneider" <pfpschneider@gmail.com>
> >> To: kcoyle@kcoyle.net, public-data-shapes-wg@w3.org
> >> Date: 03/03/2016 12:16 PM
> >> Subject: Re: SHACL syntax and metamodel complexity
> >>
> >> On 03/01/2016 09:20 PM, Karen Coyle wrote:
> >> >
> >> >
> >> > On 3/1/16 10:11 AM, Peter F. Patel-Schneider wrote:
> >> >> in a simple extension of the current SHACL RDF syntax this would 
be
> >> >>
> >> >>       [ a sh:propertyConstraint ;
> >> >>         sh:predicate ex:p ;
> >> >>         sh:minCount 1 ;
> >> >>         sh:class ex:c ;
> >> >>         sh:maxCount 5 ;
> >> >>         sh:class ex:d ;
> >> >>         sh:minCount 3 ]
> >> >
> >> > Doesn't this require that there be order among the triples?
> >> Otherwise, how do
> >> > the two minCount's apply to the correct sh:Class triple?
> >> >
> >> > kc
> >>
> >> No.  This is not a qualified cardinality.  What this says is that
> >> there is at least one value for ex:p, that all values for ex:p 
> belong to ex:c,
> >> that there are at most 5 values for ex:p, that all values for 
> ex:p belong to
> >> ex:d, and that there are at least three values for ex:p.
> > 
> > Ok, but the two minCounts are confusing. The first one (sh:minCount 1) 
is
> > essentially overridden by the second (sh:minCount 3), right? So, why 
did you
> > choose to have them both? What's the significance?
> > --
> > Arnaud  Le Hors - Senior Technical Staff Member, Open Web Technologies 
- IBM
> > Software Group
> 
> Right now, the SHACL syntax does not allow multiple minCounts, or 
multiple
> sh:class, or multiple anything.  Multiple minCounts are not useful. 
Multiple
> sh:class values are, however, and I view this as something that is going 
to be
> a pain point.
> 
> Why are multiple sh:class values not allowed?  Well, multiples are hard 
to
> deal with if they are like the current design of qualified cardinality, 
where
> there are two property values that need to be combined.  So to permit 
the
> useful multiples one has to find a way to get around the combinations.
> 
> The combinations are also problematic from a syntax viewpoint, as it may 
be
> hard to see the combination.  Thus my proposal is to refactor these 
syntactic
> constructs.  The result allows for repetition where useful and permits 
it even
> when it is not (very) useful.  Will users ever have multiple minCounts 
(on
> purpose)?  Probably not, but forbidding them doesn't seem like a good 
idea.
> 
> peter
> 
Received on Thursday, 3 March 2016 23:23:06 UTC

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