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Re: shapes and classes: different

From: Peter F. Patel-Schneider <pfpschneider@gmail.com>
Date: Mon, 26 Jan 2015 10:20:50 -0800
Message-ID: <54C68582.2070808@gmail.com>
To: Irene Polikoff <irene@topquadrant.com>, Jerven Tjalling Bolleman <jerven.bolleman@isb-sib.ch>
CC: RDF Data Shapes Working Group <public-data-shapes-wg@w3.org>
Hash: SHA1

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.


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
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Received on Monday, 26 January 2015 18:21:20 UTC

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