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Re: Need example of a River class being used as an individual ... anyone?

From: Enrico Franconi <franconi@inf.unibz.it>
Date: Mon, 10 Mar 2003 22:33:57 +0100
To: "Roger L. Costello" <costello@mitre.org>, <www-rdf-logic@w3.org>
Message-ID: <BA92C355.8E5A%franconi@inf.unibz.it>

On 3/10/03 6:15 PM, Roger L. Costello wrote:
>  Can you think of a more compelling example?  /Roger

Consider the class "Rivers" as having properties like "inRegion",
"averageLenght", and "totalNumber". Each instance of this class is the group
of rivers in a specific region; each instance would have specified the
average length of the rivers in the group and their total number.
So, for example, an instance of "Rivers" can be "RiversInSicily", having the
property "inRegion" set to the value "Sicily", and specific numbers as
values of the properties "averageLenght" and "totalNumber".
"RiversInSicily" (which is an instance of the class "Rivers") can itself be
seen as the class of all the rivers in Sicily; properties of this class can
be the name of the river and its length. An instance of the class
"RiversInSicily" could be the "SalsoRiver", with value "Salso" for the
property "name" and value 150km for the property "length".
Obviously you may want to write a constraint saying that the count of the
rivers which are instances of "RiversInSicily" (seen as class) is equal to
the value of the property  "totalNumber" of "RiversInSicily" (seen as
instance), and that the average of the lenghts of the rivers which are
instances of "RiversInSicily" (seen as class) is equal to the value of the
property "averageLenght"  of "RiversInSicily" (seen as instance).

This stuff goes back at least to the good old days of Telos (for its
theoretical foundations):
John Mylopoulos, Alexander Borgida, Matthias Jarke, Manolis Koubarakis:
Telos: Representing Knowledge About Information Systems. TOIS 8 (4): 325-362

and to KEE (for its practical successful implementation):
The Role of Frame-Based Representation in Reasoning, R.Fikes et al, CACM
28(9):904- 920 (Sept 1985).

-- e.

Enrico Franconi                  - franconi@inf.unibz.it
Free University of Bozen-Bolzano - http://www.inf.unibz.it/~franconi/
Faculty of Computer Science      - Phone: (+39) 0471-315-642
I-39100 Bozen-Bolzano BZ, Italy  - Fax:   (+39) 0471-315-649
Received on Monday, 10 March 2003 16:34:36 UTC

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