W3C home > Mailing lists > Public > semantic-web@w3.org > February 2014

Re: Deduced property

From: Krzysztof Janowicz <janowicz@ucsb.edu>
Date: Sun, 2 Feb 2014 15:50:46 -0800
Message-ID: <52EED9D6.9020801@ucsb.edu>
To: エリクソン トーレ <t-eriksson@so.taisho.co.jp>, "tim.glover@bt.com" <tim.glover@bt.com>
CC: "semantic-web@w3.org" <semantic-web@w3.org>
>> A good explanation for software engineers might be that OWL does strong duck typing.
>> Strong in the sense that the classes of an instance are defined by its properties.
>> Then they can probably extrapolate any consequences of this and arrive at OWL logic.

Duck typing typically refers to the fact that the methods and 
properties/variables of a given object determine its type. You can infer 
class membership in OWL as well as subclass relations but you can also 
explicitly declare them so this is where the analogy breaks.

[And this all is not even mentioning OWA. I agree with Aidan here: There 
are, of course, common features but also many different features and, 
thus, one should not mix inheritance in OOM with the formal semantics of 
relations such as subClass and SubPropertyOf on the SW.]

Best,
Krzysztof


On 02/02/2014 03:22 PM, エリクソン トーレ wrote:
>> From: tim.glover@bt.com, February 01, 2014 1:21 AM
>> As a software engineer, the striking difference is this.  In Java, if a class
>> A  has property x, then all objects of that class have property x. If class
>> B extends A, then all objects of class B also have property x.
>>
>> In OWL the logical direction  is completely different. In OWL, if property
>> x has domain A, that does NOT mean that all objects of class A have property
>> x. It means that IF an object has property x, it must belong to class A (very
>> roughly speaking -  I am aiming for conceptual intuition of the difference
>> here, rather than strict accuracy). IF B is a subclass of A, and IF I can
>> deduce that object b is a B, then it must also be an A.
>
> A good explanation for software engineers might be that OWL does strong duck typing.
> Strong in the sense that the classes of an instance are defined by its properties.
> Then they can probably extrapolate any consequences of this and arrive at OWL logic.
>
> Tore
>


-- 
Krzysztof Janowicz

Geography Department, University of California, Santa Barbara
5806 Ellison Hall, Santa Barbara, CA 93106-4060

Email: jano@geog.ucsb.edu
Webpage: http://geog.ucsb.edu/~jano/
Semantic Web Journal: http://www.semantic-web-journal.net
Received on Sunday, 2 February 2014 23:51:19 UTC

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