[JS] In short, the distinction between intension and extension
is fundamental to ontology, and it *must* be highlighted.
The word 'class' would hopelessly confuse the issue. (01)
[BS] I prefer: the distinction between type and instance, and thus also
between type and extension (= class of instances) is fundamental to
ontology, and I hope it will be taken as seriously as it deserves to
be taken. The word 'class' would hopelessly confuse the issue. (02)
Completely wrong conclusions. Rather such messages confuse the clear enough
To see the extension and intension difference [determining the distinction
of the ontology of entity classes and taxonomy of types], above all, one
needs to learn to tell apart two basic modes of meaning [signification for
words], known as the first and second imposition of terms [words]; namely:
1. as words signifying things, realities , existences, objects,
2. as words sygnifying just ideas, formal concepts, logical predicates,
attributes, etc.[intension]. (04)
For instance, in the sentence ''man is a living being'', the subject is used
to name a piece of reality, a living being of a certain type, while in the
sentence ''man is a human species'', the subject is used in the second
intention, symbolizing just a logical classification.
This implies that Ontology of classes [intended to represent (map) reality
or the world as the universal class of all kinds of things] operates with
the class of words standing for the kinds of realities (substances, states,
processes, etc.). Accordingly, ontology classifies things, determines
distinctions, and identifies entities only with respect to the classes of
relationships having real meanings, such as the part-whole relations,
space-relations, time-relations, or causal relations. (05)
On the contrary, the taxonomy of types works with formal objects and logical
classifications and conceptual notions such as used in set theoretical and
logical taxonomies and semantic web languages, and partly in bilogical
taxonomy of species, genus, order, family, etc. For to make it looks a real
classification, there are talks among biologists about genetic or
reproductive commonalities of species, etc. But, by its nature, taxonomy
arranges and orders its domain by logical casses and categories with respect
to formal relationships like as [the set inclusion relation and the set
membership relations and logical relations]. (06)
The confusion which instigated this good question of distinction arose for
some objective reasons. Most current computational ontologies are not really
ontologies, but rather logical classifications organized by formal logical
[set theoretical] relationships saying us a little about the real world, but
rather something about the creator's subjective reality, personal experience
and intuitions. As a bad consequence, by not seeing this essential
difference, many current ontologes, both upper and domain, view the entity
of relationship as a formal object. (07)
So there are a few ontologies as such in computing and programming practice,
most are rather formal logical classifications of entities, or taxonomies;
while the viable reasoning applications must be based on the models
describing real systems as pieces of reality. (08)
Now concerning Core's suggestion that ''There should then be an "OWL view"
of this core for general consumption and political buy-in.'' (09)
Actually, OWL is a source of many bad confusions, coming form its
developers' misunderstanding the nature of meaning and the ambiguity of
names, which the last version of OWL 1.1 dubbed as 'punning' (a funny play
on words) when the same name may stand for a class, an individiual, or a
property. The real reason of this again consists in the nature of words
itself and their modes of signification. (010)
What is missing here is that any class name (as the whole namespace) is
always distinguished by two types of naming:
I. naming of entities according to their nature, or intrinsic, substantial,
material, absolute, or definitive properties [intrinsic denomination];
II. the naming of things with respect to the external relationships
(relational properties) in which some thing stands to something else
[extrinsic denomination]. (011)
Regarding OWL and all other suchlike non-ontological languages and metamodel
specifications, as UML, etc., i agree with Barry's comments:
''Unfortunately the existing languages were developed and documented
for quite different purposes and quite different communities. Their
definitions do not satisfy the sorts of standards placed on ontology
work -- sometimes because they are confused; sometimes because they
are defining terms (like 'class') as these terms are used in
logico-linguistic contexts, rather than in ontological contexts.'' (012)
Azamat Abdoullaev (013)
----- Original Message -----
From: "Smith, Barry" <phismith@xxxxxxxxxxx>
To: "ONTAC-WG General Discussion" <ontac-forum@xxxxxxxxxxxxxx>
Sent: Sunday, January 22, 2006 6:38 PM
Subject: Re: [ontac-forum] Type vs. Class - last chance to vote. (014)
> At 05:26 PM 1/22/2006, you wrote:
>>Various themes have emerged from this discussion, and I'll
>>try to sort them out:
>> 1. The fundamental distinction which many of us have
>> emphasized for years is between _intension_ and
>> _extension_. To avoid prejudging the choice of
>> technical terms, I'll use the example of Rabbit vs.
>> Peter or Thumper. The intension of 'Rabbit' is
>> determined by some definition that is independent of
>> any actual rabbits, real or fictional. The extension
>> of "Rabbit" at a particular point in time consists
>> of all the rabbits that happen to exist at that time.
> If 'rabbit' refers to a type, and if rabbit instances existed before human
> beings, and if rabbits were able to recognize other instances of like type
> (e.g. for dating purposes) then the type rabbit existed before any
> definition was formulated. Talk of types should thus not rely too much on
> talk of definitions/intensions. Indeed there are many types in biomedicine
> for which definitions have not yet been supplied, and many types in all
> domains for which incorrect definitions have been (or were for many
> centuries) supplied.
>> 2. The word 'set', as used in all versions of set theory
>> for over a century, refers to the extension. Since
>> rabbits are notoriously prolific, the set of rabbits
>> at the instant you're reading this sentence is very
>> different from the set at the instant I wrote it.
>> The fact that sets are constantly being replaced by
>> new ones means that sets are not suitable for defining
>> any "meaning" that is supposed to remain constant.
>> 3. Aristotle introduced the word 'kategoria' as his term
>> for the intension,
> not true, I'm afraid;
> 'kategoria' means: that which is said (in the agora, or market);
> for Aristotle the terms was used to mean something like: 'highest type';
> Aristotle did not have our modern notion of intension
>>and that word was translated to Latin
>> as 'praedicatum'.
>> From those, we get the English words
>> 'category' and 'predicate'. The latter term has become
>> popular for the symbols used in _predicate calculus_, and
>> I would say that the defining rule for a predicate is
>> sufficiently stable to be used as the basis for drawing
>> a clear distinction between intensions and extensions:
>> - The intension of 'Rabbit' would be determined by the
>> definition of a monadic predicate rabbit(x).
>> - The extension of 'Rabbit' at time t would be the set
>> of all x at time t for which rabbit(x) is true.
> Again, when biologists (e.g.) develop large ontologies representing types,
> they do not do this by scanning their minds for corresponding definitions,
> or intensions; they look at the entities in reality, e.g. at patterns of
>> 4. If we wanted to be traditional, we could use the four-
>> syllable word 'category'. Otherwise, we could adopt
>> a one-syllable word, of which the two main contenders
>> seem to be 'type' and 'class'. The word 'set' is not
>> a contender because all technical uses are extensional.
>> 5. The word 'type' has a long history of use as a technical
>> term whose meaning was very close to its use as a common
>> English word. Unfortunately, Bertrand Russell gave it a
>> very narrow sense in logic, which caused many logicians
>> to introduce the word 'sort' with a slightly different
>> technical sense. Meanwhile computer language designers
>> adopted the word 'type' for the kinds of data structures
>> used in their systems. All these uses fall within the
>> scope of the informal senses of the word 'type', and it
>> seems possible to adopt 'type' as a generalization that
>> would include all the technical senses and most, if not
>> all of the common senses.
>> 6. In another unfortunate twist, the object-oriented group
>> adopted the word 'class' to distinguish their thingies,
>> which have associated procedures called 'methods', from
>> the more static data types of the older languages. More
>> recently the Semantic Webbers adopted 'class' for the
>> thingies used in OWL, but as Chris, Michael, and others
>> have pointed out, OWL also uses the word 'type', and
>> all of its definitions are very confused and confusing.
>> 7. Meanwhile, the word 'class' has long been used as a
>> synonym for 'set' in some versions of set/class theory.
>> In other versions of set theory, a class is something
>> that is just as extensional as a set, but too "big"
>> to be a proper set.
>>The major argument for using the word 'class' is that it has
>>been adopted by the Semantic Web movement, which currently
>>has a great deal of momentum. But one could also say that
>>the Semantic Web has also adopted the word 'type' in a way
>>that seems to be very closely linked to the word 'class'.
>>Summary, I strongly believe that the word 'class' is the
>>*worst* possible choice to represent the intensional side
>>of the distinction between intensions and extensions:
>> 1. Logicians use the word 'class' in the same extensional
>> sense as the word 'set'.
>> 2. Object-oriented programmers use the word 'class' as
>> something that has associated procedures, and that
>> is definitely *not* a meaning we want to suggest.
>> 3. The OWL group uses both 'class' and 'type' in ways that
>> are related, but it seems safe to say that there is
>> probably nobody in the OWL community who could give
>> a clear argument for any distinction between them.
>>In short, the distinction between intension and extension
>>is fundamental to ontology, and it *must* be highlighted.
>>The word 'class' would hopelessly confuse the issue.
> I prefer: the distinction between type and instance, and thus also between
> type and extension (= class of instances) is fundamental to ontology, and
> I hope it will be taken as seriously as it deserves to be taken. The word
> 'class' would hopelessly confuse the issue.
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