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Re: [ontolog-forum] Last Call: OWL 2 and rdf:text primitive datatype

To: "[ontolog-forum]" <ontolog-forum@xxxxxxxxxxxxxxxx>
From: "John F. Sowa" <sowa@xxxxxxxxxxx>
Date: Thu, 30 Apr 2009 09:31:06 -0400
Message-id: <49F9A81A.8000008@xxxxxxxxxxx>
John B,    (01)

> Now about "entity". I'm confused as to what this is used for.
> I've seen several descriptions including what JS (KR) says:
> "A pronounceable synonym for "T". It can be used as a default
>   type label for anything of that type".
> And when I look for "T", it shows up on the previous page as
> "The universal type..." just below Figure B.1 which shows <cap>T
> as the root of all entities.    (02)

The symbol that looks like a sans serif T is the usual notation
for the top of a lattice.  The upside-down sans serif T is used
as the symbol for the bottom of a lattice.    (03)

Therefore, I used that kind of T as the top of the type hierarchy
(or a lattice if the partial ordering of types is extended to
a lattice).  However, in most notations for logic, there is no
way to distinguish a ordinary capital T from the special kind
of T at the top.  Therefore, I suggested the label 'Entity'
as a synonym for that symbol.    (04)

If you are using Common Logic, you can use that label to say
that everything is an entity.  In CLIF,    (05)

    (forall (x) (Entity x))    (06)

In CGIF,    (07)

    [Entity @every]    (08)

This is equivalent to saying that if there is an x,
then x is an entity:    (09)

    [If [*x] [Then [Entity ?x] ]]    (010)

> I do see nouns ("object") and verbs ("process") in the Lattice,
> but I don't see "concept". Is it buried in there somewhere?    (011)

The types in the ontology are not words, although the character
strings used as labels are often spelled the same as English words.
In the commentary, I always write those labels in a boldface,
monospace font that begins with a capital letter.  The concept
node [Destroy], for example, could be translated to or from an
English sentence as the noun 'destruction' or the verb 'destroy'.    (012)

In my KR book and other publications, the only technical definition
I give for the word 'concept' is "a node in a conceptual graph."
In the English commentary, I also use the word 'concept' in the
same informal senses usually associated with the word.  But I
never use it in any technical sense other than "a node in a graph".    (013)

Some people use the word 'Thing' for the top of the type hierarchy,
but it has too many connotations of physical object.  It seems
odd to say that an integer, a state of happiness, or an act
of walking is a thing.    (014)

Some people use the word 'Concept' for the top of the hierarchy,
but that usage is much, much worse.  One could say that an
object, an integer, a state, or an act is *represented by*
a concept, but it is totally senseless to say that they *are*
concepts.    (015)

I discuss some of these and other issues in the papers included
in the Guided Tour of Ontology:    (016)

    http://www.jfsowa.com/ontology/guide.htm    (017)

John Sowa    (018)

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