Re: shapes-ISSUE-91 (hsolbrig): Default Cardinality [SHACL Spec]

Yes, I agree that there should be a statement about engines not supporting inferencing, shapes must be stated explicitly.

If the no maxCount constraint means unlimited or unconstrained, why does it need to be expressed?

Sent from my iPhone

> On Sep 28, 2015, at 4:26 AM, Eric Prud'hommeaux <eric@w3.org> wrote:
> 
> * Dimitris Kontokostas <kontokostas@informatik.uni-leipzig.de> [2015-09-28 10:02+0300]
>> On Mon, Sep 28, 2015 at 1:17 AM, Arthur Ryman <arthur.ryman@gmail.com>
>> wrote:
>> 
>>> I vote -1 to defining optional values for any constraint.
>>> 
>>> The current design is consistent in its treatment of absent
>>> constraints, namely that they do not lead to any checks. It is
>>> therefore inconsistent to say that if minCount or maxCount are absent
>>> then they are in effect present with some default value. If is
>>> especially inconsistent to assign default values that give a result
>>> different than if the constraints were absent.
>> 
>> I agree with Arthur here, all constraints should be explicitly stated in
>> the SHACL graph.
> 
> The usual motivation for no-defaults is that what you learn from
> inferencing can contradict what you understood with less or no
> inferencing. A screw case in our example would be:
> 
>  my:minCard owl:samePropertyAs sh:minCount .
>  my:FooShape sh:property [
>      sh:predicate foaf: name ;
>      my:minCard 2       # ooo, sneaky
>    ] .
> 
> You'll note, however, that this screw case arises regardless of
> whether the default min cardinality is 0 or 1. I think we should just
> say "a SHACL engine is not expected to perform any inferencing" and
> pick defaults that are attractive to folks working in e.g. JSON-LD.
> 
> I maintain my support for default [1..1] cardinality. Regardless, we
> need a way to express an unlimited max cardinality.
> 
> 
>> - Dimitris
>> 
>> 
>> 
>> -- 
>> Dimitris Kontokostas
>> Department of Computer Science, University of Leipzig & DBpedia Association
>> Projects: http://dbpedia.org, http://http://aligned-project.eu,
>> http://rdfunit.aksw.org
>> Homepage:http://aksw.org/DimitrisKontokostas
>> Research Group: http://aksw.org
> 
> -- 
> -ericP
> 
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Received on Monday, 28 September 2015 14:25:55 UTC