17 January 2009


Ontology: makes me dizzy. Ontology means everything. Everything.

Ontology \On*tol"o*gy\, n. [Gr. ? the things which exist
(pl.neut. of ?, ?, being, p. pr. of ? to be) + -logy: cf. F.
1. That department of the science of metaphysics which
investigates and explains the nature and essential
properties and relations of all beings, as such, or the
principles and causes of being.
[1913 Webster]

2. (Computers) A systematic arrangement of all of the
important categories of objects or concepts which exist in
some field of discourse, showing the relations between
them. When complete, an ontology is a categorization of
all of the concepts in some field of knowledge, including
the objects and all of the properties, relations, and
functions needed to define the objects and specify their
actions. A simplified ontology may contain only a
hierarchical classification (a {taxonomy}) showing the
type subsumption relations between concepts in the field
of discourse. An ontology may be visualized as an abstract
graph with nodes and labeled arcs representing the objects
and relations.

Note: The concepts included in an ontology and the
hierarchical ordering will be to a certain extent
arbitrary, depending upon the purpose for which the
ontology is created. This arises from the fact that
objects are of varying importance for different
purposes, and different properties of objects may be
chosen as the criteria by which objects are classified.
In addition, different degrees of aggregation of
concepts may be used, and distinctions of importance
for one purpose may be of no concern for a different

-- From The Collaborative International Dictionary of English v.0.48

n : the metaphysical study of the nature of being and existence

-- From WordNet (r) 2.0

28 Moby Thesaurus words for "ontology":
aesthetics, axiology, casuistry, cosmology, epistemology, ethics,
existentialism, first philosophy, gnosiology, logic,
mental philosophy, metaphysics, moral philosophy, phenomenology,
philosophastry, philosophic doctrine, philosophic system,
philosophic theory, philosophical inquiry,
philosophical speculation, philosophy, school of philosophy,
school of thought, science of being, sophistry, theory of beauty,
theory of knowledge, value theory

-- From Moby Thesaurus II by Grady Ward, 1.0


1. <philosophy> A systematic account of Existence.

2. <artificial intelligence> (From philosophy) An explicit
formal specification of how to represent the objects, concepts
and other entities that are assumed to exist in some area of
interest and the relationships that hold among them.

For {AI} systems, what "exists" is that which can be
represented. When the {knowledge} about a {domain} is
represented in a {declarative language}, the set of objects
that can be represented is called the {universe of discourse}.
We can describe the ontology of a program by defining a set of
representational terms. Definitions associate the names of
entities in the {universe of discourse} (e.g. classes,
relations, functions or other objects) with human-readable
text describing what the names mean, and formal {axioms} that
constrain the interpretation and well-formed use of these
terms. Formally, an ontology is the statement of a {logical

A set of {agents} that share the same ontology will be able to
communicate about a domain of discourse without necessarily
operating on a globally shared theory. We say that an agent
commits to an ontology if its observable actions are
consistent with the definitions in the ontology. The idea of
ontological commitment is based on the {Knowledge-Level}

3. <information science> The hierarchical structuring of
knowledge about things by subcategorising them according to
their essential (or at least relevant and/or cognitive)
qualities. See {subject index}. This is an extension of the
previous senses of "ontology" (above) which has become common
in discussions about the difficulty of maintaining {subject


-- From The Free On-line Dictionary of Computing (27 SEP 03)

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