Re: "shape" as a relationship, not a class

On Sat, Feb 21, 2015 at 1:04 AM, Holger Knublauch <holger@topquadrant.com>
wrote:

>
> On 2/21/15 1:15 AM, Arthur Ryman wrote:
>
>> Holger Knublauch <holger@topquadrant.com> wrote on 02/08/2015 05:36:32
>> PM:
>>
>>  ... I am afraid the distinction
>>> between real-world objects and their representation drifts into
>>> theoretical realms that nobody outside of the RDF world seems to care
>>> about (and rightfully so).
>>>
>>
> My above statement was in response to a previous statement in the thread
> that
>
> > It seems to me that the key difference between shapes and classes is
> > exactly this: a shape is information about a graph; a class is
> > information about the RWO.
>
> To highlight why this distinction is problematic, look no further than
> SHACL itself.
>
>     sh:Shape rdf:type rdfs:Class .
>
>     ex:MyShape rdf:type sh:Shape .
>
> Shapes are not RWOs. There are similar examples everywhere.
>
> Should it instead be
>
>     ex:MyShape sh:nodeShape sh:Shape ?
>
> Then, what would sh:Shape be?
>
>     sh:Shape sh:nodeShape sh:Shape ?
>
> Welcome to a parallel semantic web that may become an even smaller niche
> than the current semantic web, and meanwhile confuses newcomers to the
> class-based semantic web even more.
>

+1
Maybe it will take some time but when foaf declares a foaf:PersonShape

    :x sh:instanceShape foaf:PersonShape

will bring the same issues some people argue about

    :x a foaf:Person

So, although I still don't like assigning shapes directly to classes,
sh:instanceShape doesn't solve this issue

Best


>
> Regards,
> Holger
>
>
>
>  Holger,
>>
>> The distinction is important in some cases because if you fail to make the
>> distinction, then when you read the RDF, it sounds like nonsense. The
>> classic example is the distinction between a person and a user account
>> owned by that person. A person is a RWO and should have a URI that is
>> different that the user account, which is an information resource (a web
>> document).
>>
>> A web document can have properties such as creator (a person), creation
>> date, modification date, etc. It makes sense to say that a user account
>> document has a modification date, but it is nonsense to say that the
>> person who owns the user account has that modification date (barring
>> coincidental plastic surgery on that date). FOAF makes this clear. This
>> whole topic is nicely discussed in [1], which is co-authored by your
>> newest colleague.
>>
>> [1] http://www.w3.org/TR/cooluris/
>>
>>
>>
>
>


-- 
Dimitris Kontokostas
Department of Computer Science, University of Leipzig
Research Group: http://aksw.org
Homepage:http://aksw.org/DimitrisKontokostas