John, thank you, that's just right! (01)
Christopher (02)
----- Original Message -----
From: "John F. Sowa" <sowa@xxxxxxxxxxx>
To: "[ontolog-forum]" <ontolog-forum@xxxxxxxxxxxxxxxx>
Sent: Thursday, August 28, 2008 3:34 PM
Subject: Re: [ontolog-forum] Thing and Class (03)
> 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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