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RE: shapes and classes: different

From: Irene Polikoff <irene@topquadrant.com>
Date: Mon, 26 Jan 2015 14:04:34 -0500
To: "'Peter F. Patel-Schneider'" <pfpschneider@gmail.com>, "'Jerven Tjalling Bolleman'" <jerven.bolleman@isb-sib.ch>
Cc: "'RDF Data Shapes Working Group'" <public-data-shapes-wg@w3.org>
Message-ID: <19a201d0399a$ed881650$c89842f0$@topquadrant.com>
< Saying that a square is subclass of a rectangle and that squares have their width and breadth equal doesn't make square a shape>

<Saying that squares are precisely those rectangles whose width and breadth are equal does make square a shape>

For practical purposes, what is the difference?

-----Original Message-----
From: Peter F. Patel-Schneider [mailto:pfpschneider@gmail.com] 
Sent: Monday, January 26, 2015 1:21 PM
To: Irene Polikoff; Jerven Tjalling Bolleman
Cc: RDF Data Shapes Working Group
Subject: Re: shapes and classes: different

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The defining characteristic of shapes is that they are provided with conditions that determine which objects belong to them.  Saying that a square is subclass of a rectangle and that squares have their width and breadth equal doesn't make square a shape even though it may be the case that objects belonging to square are precisely those objects that have an rdf:type link to  it. Saying that squares are precisely those rectangles whose width and breadth are equal does make square a shape as this provides a set of conditions that determine when an object is a square.

peter


On 01/26/2015 09:24 AM, Irene Polikoff wrote:
>> Your word shape is my word owl:Class.
> 
> +1
> 
> So, the simplest solution is not to have a new thing called Shape.
> 
> Another option may be to use it as a type so that some classes can be 
> of type Shape as well as Class.
> 
> This seems to be unnecessary though as every class is already a shape.
> At minimum, even if there are no other constraints declared for a 
> class, it says that all instances belonging to it must have a certain 
> type triple. If there is a class :Person, then its instances must have
> :Person1 a ::Person triple (whether it is asserted or inferred, 
> doesn't matter). A very minimalistic data shape, but still a shape.
> 
> Irene
> 
> On Jan 26, 2015, at 11:12 AM, Jerven Tjalling Bolleman 
> <jerven.bolleman@isb-sib.ch <mailto:jerven.bolleman@isb-sib.ch>> wrote:
> 
>> I really can't help myself...
>> 
>> On 26/01/15 15:12, Peter F. Patel-Schneider wrote:
> The most important aspect of classes is that you state that objects 
> belong to them.  If you don't state that objects belong to X, X is not 
> a class.
> 
> The most important aspect of shapes is that you provide conditions
> stating precisely when an object belongs to them.   If you don't provide
> conditions stating precisely when an object belongs to X, X is not a 
> shape.
> 
> Having shapes also be classes implies that you state that objects 
> belong to shapes.  Having classes also be shapes implies that you 
> provide recognition conditions for classes. Both situations are 
> possible, but both have consequences.
>>> Your word shape is my word owl:Class. Allowing class membership 
>>> inference from recognition conditions is as normal as class member 
>>> ship assertion directly in the data. But I am absolutely 
>>> flabbergasted that I am having this argument with one of the OWL2 
>>> editors!
>>> 
>>> Basically I am reading your response as class membership only 
>>> inferred is "shape membership". Class membership asserted is not 
>>> "shape membership". Or paraphrased: Shapes only allows triples with 
>>> the shape:member predicate (IMO equivalent to rdf:type) to be 
>>> inferred and not asserted.
>>> 
>>> 
> 
> peter
>>> 
>> 
>> -- ------------------------------------------------------------------- 
>> Jerven Bolleman                        Jerven.Bolleman@isb-sib.ch 
>> <mailto:Jerven.Bolleman@isb-sib.ch> SIB Swiss Institute of 
>> Bioinformatics  Tel: +41 (0)22 379 58 85 CMU, rue Michel Servet 1
>> Fax: +41 (0)22 379 58 58 1211 Geneve 4, Switzerland     www.isb-sib.ch
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>> Follow us at https://twitter.com/#!/uniprot
>> -------------------------------------------------------------------
>> 
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Received on Monday, 26 January 2015 19:05:11 UTC

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