Re: type and instance and subclass in SHACL documents

The SHACL documents talk about instance.  If this is RDFS instance, then, yes,
SHACL engines would always have to treat rdfs:label as an instance of
rdf:Property.

This is why I say that the SHACL documents should be very clear every time
that they talk about instance that it is not the common RDFS instance that
they are talking about but some new notion particular to SHACL, particularly
as SHACL uses RDFS vocabulary.

SHACL instance is indeed very different from RDFS instance.

peter


On 03/12/2016 10:05 AM, Irene Polikoff wrote:
> We need rdf:type to know if something is an instance of a class (note that I am saying simply 'instance' because I do not see the difference).
> 
> If {rdfs:label rdf:type rdf:Property} triple was provided to a SHACL engine, then the violation would be raised.
> 
> How else could it be known from the data graph that rdfs:label is a property? Or are you saying that SHACL engines should always include triples in RDFS vocabulary when they do their processing? 
> 
> Sent from my iPhone
> 
>> On Mar 11, 2016, at 10:36 PM, Peter F. Patel-Schneider <pfpschneider@gmail.com> wrote:
>>
>> Using the RDFS definition of instance, rdfs:label is an instance of
>> rdf:Property so it is in the scope of the shape and there is a violation.
>> Using the SHACL definition of instance, rdfs:label is *not* an instance of
>> rdf:Property so it is *not* in scope and there is *no* violation.
>>
>> peter
>>
>>
>>> On 03/11/2016 04:50 PM, Karen Coyle wrote:
>>> Peter, I admit that I, too, am having trouble understanding this. (And so it
>>> isn't all on Peter, if anyone else "gets it" maybe they could weight in.) The
>>> SHACL document uses the term "instance" 78 times. I admit I only looked at the
>>> first couple of dozen of those uses. For the most part they appear to me to
>>> conform to the RDFS definition of "instance" - meaning an instance of class.
>>> In some cases the term is used more colloquially, but those places in the
>>> document don't seem to be definitional.
>>>
>>> You say that it doesn't validate, but can you say what the difference is in
>>> the two definitions? I still see it as having to do with the vocabulary
>>> definition as opposed to the SHACL validation, but you didn't buy that when I
>>> suggested it. If I were to use a typical OWL-based validation, rdfs:range
>>> ex:label "range" would be flagged as inconsistent. The same would be true if I
>>> would have
>>>  ex:someSubject dct:type "text" .
>>> (dct:type has a range of rdf-schema#Class)
>>>
>>> If this isn't the issue, I would sure like to know what is.
>>>
>>> Thanks,
>>> kc
>>>
>>>> On 3/11/16 2:22 PM, Peter F. Patel-Schneider wrote:
>>>> The definition of SHACL depends on "instance".  This can be read to mean
>>>> "RDFS instance" or "SHACL instance".  Under the former meaning the data graph
>>>> does not validate against the shape.   Under the latter meaning the data graph
>>>> does validate against the shape.
>>>>
>>>> peter
>>>>
>>>>
>>>>> On 03/11/2016 02:15 PM, Irene Polikoff wrote:
>>>>> I don¹t understand what you mean by
>>>>>
>>>>> "validates against this shape under SHACL instance but not under RDFS
>>>>> instance.²
>>>>>
>>>>> I am not able to parse the sentence.
>>>>>
>>>>> What are you doing? Taking a shape described and the graph described and
>>>>> running it against SHACL engine? What execution validates and what
>>>>> execution doesn¹t validate?
>>>>>
>>>>>
>>>>>
>>>>> Irene
>>>>>
>>>>>
>>>>>
>>>>> On 3/11/16, 5:03 PM, "Peter F. Patel-Schneider" <pfpschneider@gmail.com>
>>>>> wrote:
>>>>>
>>>>>>> On 03/11/2016 01:01 PM, Karen Coyle wrote:
>>>>>>>
>>>>>>>
>>>>>>>> On 3/11/16 11:43 AM, Peter F. Patel-Schneider wrote:
>>>>>>>> Consider the following shape (using obvious prefix declarations)
>>>>>>>>
>>>>>>>> sh:propertyShape a sh:Shape ;
>>>>>>>>   sh:scopeClass rdf:Property ;
>>>>>>>>   sh:property [ sh:predicate rdfs:label ;
>>>>>>>>                 sh:minCount 1 ] .
>>>>>>>>
>>>>>>>> The data graph (using obvious prefix declarations)
>>>>>>>>
>>>>>>>> rdfs:range ex:label "range" .
>>>>>>>>
>>>>>>>> validates against this shape under SHACL instance but not under RDFS
>>>>>>>> instance.
>>>>>>>
>>>>>>> Isn't this a problem with every vocabulary and not just RDFS? If the
>>>>>>> rules of
>>>>>>> the vocabulary (such as domain and range) are not encoded as such in
>>>>>>> SHACL
>>>>>>> then the SHACL result can be "in violation" of the vocabulary
>>>>>>> definition.
>>>>>>>
>>>>>>> Now, if that is the case then I understand that violating the foundation
>>>>>>> vocabulary of RDF/RDFS may be more grave than violating a user-developed
>>>>>>> vocabulary, and in some cases doing the latter may indeed be the
>>>>>>> intention of
>>>>>>> the SHACL definition. So do we want to build into SHACL that it must
>>>>>>> follow
>>>>>>> RDF/RDFS property and class definitions? And how feasible is that?
>>>>>>>
>>>>>>> kc
>>>>>>
>>>>>> This is only a real problem because SHACL uses "instance" in its
>>>>>> specification, this term is also used centrally in RDFS, and SHACL uses
>>>>>> RDFS
>>>>>> vocabulary.
>>>>>>
>>>>>> The question then is how to read "instance" in SHACL documentation, i.e.,
>>>>>> how
>>>>>> to prevent readers of the SHACL documentation from seeing "RDFS instance"
>>>>>> where "SHACL instance" is meant.
>>>>>>
>>>>>>
>>>>>> peter
>>

Received on Saturday, 12 March 2016 21:30:53 UTC