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Re: type and instance and subclass in SHACL documents

From: Holger Knublauch <holger@topquadrant.com>
Date: Tue, 8 Mar 2016 08:36:19 +1000
To: public-data-shapes-wg@w3.org
Message-ID: <56DE0263.70505@topquadrant.com>
On 8/03/2016 1:51, Peter F. Patel-Schneider wrote:
> On 03/06/2016 08:46 PM, Holger Knublauch wrote:
>> Thanks for the feedback, Peter. I have tried to address it here:
> [...]
>
>> On 7/03/2016 6:59, Peter F. Patel-Schneider wrote:
>>> General
> [...]
>
>>> It is not sufficient to say in 1.1 that SHACL has unique versions of types
>>> and instances.  These notions are in very widespread use.  Each time that
>>> SHACL deviates from the common, accepted W3C practice it should be called
>>> out, e.g., "SHACL type" or "SHACL instance".
>> I hope this doesn't need to be repeated each time as this may render the
>> document harder to read. Furthermore, the terms "SHACL type" and "SHACL
>> instance" would first need to be formally defined too.
>>
>> Instead, I suggest we should define what "type", "instance" and "subclass"
>> mean in the remainder of the document. I have put a corresponding terminology
>> block at the end of section 1.1
> This is inadequate.
>
> SHACL uses RDF graphs and RDFS vocabulary.  There are already definitions of
> type and instance and subclass that come from RDF and RDFS.  SHACL needs to
> differentiate its version of type and instance and subclass from these
> dominant notions and this can only be reliably done by qualifying them each
> time they appear in formal SHACL documents.
>
> Alternatively the SHACL document could use different words for these
> relationships or could restrict the inputs that it handles so that it uses the
> dominant versions of type and instance and subclass.

My interpretation of the situation is

- RDF and RDFS define the IRIs of vocabulary terms rdf:type and 
rdfs:subClassOf
- terms like subclass, type and instance already existed before RDFS and 
carry intuitive meaning
- there is no need to over-complicate a situation that is already clear 
to most readers

The only difference between our definitions of the terms is that you 
think that subclassing must always require inferences (domain, ranges 
etc). I believe these concepts are orthogonal. Some rdfs:subClassOf 
triples may be the result of inferencing, but it doesn't matter to SHACL 
where they came from. As long as we make this clear in the beginning, I 
hope we can keep the document intuitive and not over-complicate it.

Holger
Received on Monday, 7 March 2016 22:36:55 UTC

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