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[UNITS] FAQ : Constraints on data values range

From: Bernard Vatant <bernard.vatant@mondeca.com>
Date: Fri, 9 Apr 2004 17:50:42 +0200
To: "SWBPD" <public-swbp-wg@w3.org>
Message-ID: <GOEIKOOAMJONEFCANOKCOEDDDMAA.bernard.vatant@mondeca.com>


I have not noticed any activity under [UNITS] so far ... this is a first bait :))

A FAQ in Protégé-OWL list, I'll give here the latest variant sent yesterday (summed up)

"I have defined a class 'Wheel'
and a DatatypeProperty 'diameterValue'
on Domain 'Wheel'
and Range 'Integer'

I want to create a class 'BigWheel' with a restriction on the property
'diameterValue', for instance 'diameterValue => 10'.

How do I do that in OWL?"

I had answered that basically you can't express that kind of 'quantitative restriction' in
OWL, although there are workarounds, like using a 'minDiameterValue' property and so on.

I guess every other user wanting to include units in one's ontology will hit that kind of
wall.

It figures we should come out with clear explanations why OWL does not support
quantitative restrictions on DatatypeProperty with numerical Range, and more generally
restrictions linked to the very nature of data themselves, like defining the class
'WellDescribedThing' by restriction on a 'description' value to 'over 1000 words'.

[Seems to me that there are many ways to work around declaration of those kinds of
restrictions, but that OWL internally makes no provision to check their consistency, but
can be used to pass them as black boxes to external applications that can make sense of
them. IOW, I can declare an instance of 'BigWheel' with 'diameterValue' set to 9.7, no
inconsistency will be detected by pure logical tools with 'minDiameterValue = 10', but
external applications able to deal with quantities will make sense of it.]

Bernard Vatant
Senior Consultant
Knowledge Engineering
Mondeca - www.mondeca.com
bernard.vatant@mondeca.com
Received on Friday, 9 April 2004 11:50:58 UTC

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