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Re: [ontolog-forum] Thing and Class

To: "[ontolog-forum]" <ontolog-forum@xxxxxxxxxxxxxxxx>
From: Mike Bennett <mbennett@xxxxxxxxxxxxxxx>
Date: Thu, 28 Aug 2008 15:39:05 +0100
Message-id: <48B6B889.7010308@xxxxxxxxxxxxxxx>
John,    (01)

I tend to use the word "Thing" for exactly the same reasons you give. So 
many people in the space I am in are either familiar with data modelling 
or OO terminology that Entity (used in Entity Relationship Diagrams) and 
Type (type of variable in programming) are unusable. As is Class of 
course. Entity is the lest useful because so many business people have 
learnt a bit of ERM modelling and use it when they should be specifying 
a view of their reality.    (02)

People balk at first when I use "Thing" because it sounds so 
unscientific. That works in its favour because it makes it clear that 
this is not something that some bunch of technies have cooked up, but is 
a term describing the world of real physical reality. Once people 
understand that, we are in a position to start talking about real things 
rather than some perceived new programming / paradigm / general BS set 
of terms which they were expecting to hear about.    (03)

Unfortunately now that OWL is becoming well known among the technical 
community, Thing will probably go the same way as the rest.    (04)

Also people tend to assume that a "Thing" must be a concrete, 
independent, continuant thing, when in fact it can be concrete or 
abstract, continuant or occurrent, and independent, relative or 
mediating. Having all those categories of thing does stretch the 
natural-language use of the word Thing, I admit. But I feel it's still 
the word with the least extraneous associations either among technical 
people or among business people who have had to deal with technical 
people over the years. Which pretty much covers everyone you need to 
talk to about ontologies.    (05)

Mike    (06)

John F. Sowa wrote:    (07)

>Azamat and Antoinette,
>Developing a good meta-level ontology for talking about ontology
>and its relationship to various applications is important, and
>poor choices can lead to endless confusion.  (Even initials can
>lead to confusion when they're ambiguous, e.g. AA in this case.)
>Azamat> The interrelations of classes as well as classes and things
> > are actually more subtle and deep, than generally presented in
> > various specifications...
>I certainly agree.
>Antoinette> I consider, that in this common world, people are NOT
> > things. People place or thing...
>There is a time-honored international terminology for logic and
>ontology that was derived from Greek and Latin.  Some people have
>objected because the terms are often long and unfamiliar.
>One such word is 'entity' from Latin 'entitas', which literally
>means anything that exists.  It does not have any associated
>baggage of familiar associations, and it can be associated with
>cognate terms in many other languages.  If some languages don't
>have a native word for 'entity', they can just borrow 'entitas'.
>The word 'thing', however, has too many familiar associations,
>and the corresponding familiar terms in other languages have
>different associations.  Therefore, it is very hard to translate
>the word 'thing' to rough equivalents in multiple languages
>without creating different confusions in each language.
>The word 'class' is another term that creates multiple confusions
>because it also has multiple and confusingly different meanings
>in mathematics, programming languages, and common English usage:
>  1. In mathematics, the word 'class' is sometimes used as a synonym
>     for set by some authors, and it is sometimes used as a term
>     for a set-like collection that is too big to be a proper set.
>  2. In object-oriented programming languages, the word 'type' was
>     commonly used for data types.  But the OO languages introduced
>     a kind of entity that was different from a traditional datatype
>     because it had associated procedural "methods".
>  3. In common English usage, the word class is used confusingly in
>     ways that are synonyms for 'set' and in ways that are synonyms
>     for 'type'.  For example, one could talk about the class of
>     students in a room or the set of students.  But there are other
>     uses that refer to the type rather than any particular set,
>     as in 'middle class', 'upper class', or 'first class'.
>Some time ago, we had had a discussion on this list about whether
>we should use the term 'type' or 'class' for the categories of an
>ontological hierarchy.  Both Barry Smith and I were strongly urging
>people to use the word 'type' rather than 'class', but many others
>wanted to use 'class' because it was, unfortunately, used in OWL.
>There was a vote, and the word 'type' won.  But there was a lot
>of grumbling by people who were using OWL.
>I believe that the OWL developers made a very serious mistake in
>adopting the term 'class' because of its association with OO languages.
>That should have been a strong argument against using the word 'class'
>because ontological categories are very different from OO classes.
>But the main reason for not using the word 'class' is its association
>with the purely extensional set theory:  a set (or class) is uniquely
>defined by its instances.  A type, however, is an intensional term,
>and two types may be distinct even when they have exactly the same
>instances (or no instances at all).
>For example, the empty set is a subset of every other set.  The set
>of unicorns is empty; therefore, it is a subset of the set of cows.
>But the type Unicorn is very different from the type Cow.  Other
>examples, include the set of all human beings and the set of all
>featherless bipeds.  Today, those sets are the same, but the types
>have very different definitions.
>Many dinosaurs, such as T. Rex, were bipeds.  Some of them had
>feathers, but no one knows whether they all had feathers.  But
>if some of them didn't, it would be a mistake to call them
>human beings.
>So I recommend that we drop the words 'thing' and 'class' when
>talking about ontologies, and use the terms 'entity' and 'type'.
>John Sowa
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>    (08)

Mike Bennett
Hypercube Ltd. 
89 Worship Street
London EC2A 2BF
Tel: 020 7917 9522
Mob: 07721 420 730
www.hypercube.co.uk    (09)

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