RE: OWL 2.0 ...

Hans, I see that this discussion has evolved, but I briefly wanted to note: this discussion is quite interesting, but it is about ontology content, not about representational frameworks (languages, reasoning rules and such). 
 
On the matter of content, I am still in disagreement with your take on things like Beethoven's 5th: I do make that difference, but it is irrelevant. LVB didn't author either one occurrence (whether executed in Milan, Vienna or wherever) or a class of occurrences. He authored a musical work, which can be executed in many times and many places.  One conception of this is that this is an individual thing; if it is, though, it doesn't seem to be the kind of thing that has, plausibly, spatial location.  You can of course stipulate, in an ontology, that 'individuals' have spatio-temporal placement.  The question then is whether that ontology should be adopted or not.
 
(I don't think, btw, that this is just an instance of the 3d/4d debate.)
 
Regards, 


________________________________

	From: public-owl-dev-request@w3.org [mailto:public-owl-dev-request@w3.org] On Behalf Of Hans Teijgeler
	Sent: Friday, April 15, 2005 3:26 AM
	To: public-owl-dev@w3.org
	Cc: Matthew West; Valen-Sendstad, Magne
	Subject: RE: OWL 2.0 ...
	
	
	Pierluigi,
	 
	Let me start with an excerpt from the book "Ontological Engineering" by Asunción Goméz-Peréz, Mariano Fernández-Lopéz, and Oscar Corcho:
	QUOTE
	What are things? What is the essence that remains inside things even when they change (changes in their color, changes in their size, etc)? Do concepts (book, tree, table, etc) exist outside our mind? How can the entities of the world be classified? These are some of the questions that Ontology, the philosophy of being, has tried to answer for thousands of years. In Ontology we can distinguish between essence and existence.The essence of something is what this something is. However, an existence is to be present among things in the real world. For instance, a centaur is half a man and half a horse, so it has essence though it does not exist.
	UNQUOTE
	
	You wrote:
	<PM> This strikes me as an exquisitely ontological, or if you prefer domain-sensitive, determination
	<HT> The data model of ISO 15926-2 is as generic as it can be and is NOT domain-specific. The domain-specific aspects are introduced when linking it to a particular vocabulary (we call it a Reference Data Library). If the library is about medical classes, the information is about medical matters, if the library is about real estate stuff, it is real-estate information. How much more generic can you be? And what is wrong, in the context of OWL, with being "exquisitely ontological"?
	 
	<PM> There are plenty of individuals (in the sense in which individuals are in pricniple distinct from classes) that would not have spatio temporal presence such as you describe. 
	<HT> In our, and the above, meaning of "individual" ALL have spatio-temporal presence. It is a matter of definition and paradigm. 
	 
	<PM> There can be abstract individuals that have no particular location, though perhaps a "lifetime": ordinary examples would be, under plausible assumptions, Beethoven's 5th symphony and the "Crusoe." 
	<HT> This proves my point: you don't make a difference between Beethoven's 5th Symphony as (in our terminology) a class_of_activity and as an activity. The latter happens at a particular evening in, say, the Scala of Milano, and is a member of the class_of_activity "Beethoven's 5th Symphony", together with all the other performances in the past, present, and future.
	 
	<PM> There can be individuals that have perhaps location in abstract space, but no lifetime: the Equator, or the North Pole.  All this might be in dispute, of course.  
	<HT> The North Pole and the Equator exist in real space. I don't think that Robert Peary's expedition in 1909 travelled to something that was in abstract space. In our definition the North Pole is a spatio-temporal individual that is a "feature" of the globe (like a nose is a feature of a face), and it is classified with a class that has certain criteria for being a North Pole (mind you, the North Pole isn't at the same location all the time).
	
	<PM> The point is I don't think this belongs in a language's specification. 
	<HT> Not if you deliberately want to limit the expressivity of that language.
	 
	Regards,
	Hans
	____________________________
	Hans Teijgeler
	co-author of ISO 15926-2 <http://www.infowebml.ws/ECM4.5/ECM4.5.html> 
	author of ISO 15926-7
	website www.InfowebML.ws <http://www.infowebml.ws/> 
	e-mail hans.teijgeler@quicknet.nl
	phone +31-72-509 2005