[SCL] "ontologies"

[John F. Sowa]

Pat,

Since you prefer the usage in semantic web circles,
I will quote the definition from the "OWL Web
Ontology Language Overview" of 15 Dec 2003:

    OWL can be used to explicitly represent the meaning
    of terms in vocabularies and the relationships between
    those terms. This representation of terms and their
    interrelationships is called an ontology.

This definition has two implications for our discussion:

  1. OWL "can" be used to represent the meaning
     of terms -- in other words, there are also
     other applications for OWL.

  2. Only those applications of OWL that represent
     the meanings of terms and their relationships
     are called ontologies.

Point #2 is the primary purpose of the KL-ONE T-box
as opposed to the A-box.  But theories are more general,
since they can state A-box assertions in addition to
T-box terminologies.  Examples:  rules, constraints,
specifications, databases, knowledge bases, etc.

To get a second opinion for the field of KR, I typed
the following to Google:

    ontology "knowledge representation"

And the first hit was

    http://www.cs.man.ac.uk/~stevens/onto/

The text (copy below) defines the word in more detail,
but still with the underlying idea that an ontology
defines terms, as in the T-box, not assertions,
as in the A-box.

I completely agree with your statement:

 > And frankly, I think it is foolish to not be willing
 > to adapt to what is obviously the current term of
 > choice used throughout the rest of the world, even
 > to the point now where it is being used in journal
 > and conference titles without comment or explanation,
 > simply in order to identify a subdiscipline of
 > computer science.

So I typed both words "ontology" and "theory" into Google:

    "ontology" -- 1,140,000 hits

    "theory" -- 25,800,000 hits

Clearly, the word "theory" is the current term of choice
used throughout the rest of the world, even to the point
now where it is being used everywhere without comment
or explanation.

John
____________________________________________________

What is an Ontology?

Ontology is the study or concern about what kinds of things exist - what 
entities or `things' there are in the universe [3]. The computer science 
view of ontology is somewhat narrower, where an ontology is the working 
model of entities and interactions either generically (e.g. the Cyc 
ontology [4]) or in some particular domain of knowledge or practice, 
such as molecular biology or bioinformatics. The following definition is 
given in [5]:

`An ontology may take a variety of forms, but necessarily it will 
include a vocabulary of terms, and some specification of their meaning. 
This includes definitions and an indication of how concepts are 
inter-related which collectively impose a structure on the domain and 
constrain the possible interpretations of terms.'

Gruber defines an ontology as `the specification of conceptualisations, 
used to help programs and humans share knowledge' [6]. The 
conceptualisation is the couching of knowledge about the world in terms 
of entities (things, the relationships they hold and the constraints 
between them). The specification is the representation of this 
conceptualisation in a concrete form. One step in this specification is 
the encoding of the conceptualisation in a knowledge representation 
language. The goal is to create an agreed-upon vocabulary and semantic 
structure for exchanging information about that domain. The 
specification or encoding of an ontology will be explored in Section 5.

The main components of an ontology are concepts, relations, instances 
and axioms. A concept represents a set or class of entities or `things' 
within a domain. Protein is a concept within the domain of molecular 
biology. Concepts fall into two kinds:

    1. primitive concepts are those which only have necessary conditions 
(in terms of their properties) for membership of the class. For example, 
a globular protein is a kind of protein with a hydrophobic core, so all 
globular proteins must have a hydrophobic core, but there could be other 
things that have a hydrophobic core that are not globular proteins.

    2. defined concepts are those whose description is both necessary 
and sufficient for a thing to be a member of the class. For example, 
Eukaryotic cells are kinds of cells that have a nucleus. Not only does 
every eukaryotic cell have a nucleus, every nucleus containing cell is 
eukaryotic.