General Formal Ontology (GFO)
Several groups are tackling the development of top-level
ontologies or certain aspects of top-level
ontologies. Here, we only mention a few important approaches.
The following approaches are fairly developed, and they are used, in part,
as a source for our considerations. Nicola
Guarino, an early proponent of the use of
ontologies in the field of knowledge-based systems, is involved in the
construction of DOLCE (39,40). Further, two
other ontologies are presented in (39), following
the idea of an ontology library in the WonderWeb project. DOLCE itself
is presented as a hierarchy of categories and several relationships
between them. The description is fairly extensive and an
axiomatization is contained therein as well.
1.4 Related Work
John Sowa in (54) presents and extensively discusses a
top-level ontology in the form of a polytree
within a comprehensive book on knowledge representation issues, i.e.,
it is not a pure work introducing a top-level ontology. Sowa's ontology is
based on ideas of the philosopher Charles Sanders Peirce.
The Standard Upper Merged Ontology (SUMO) is an effort of
the P1600.1 Standard Upper Ontology Working Group at IEEE
(57). (43) provides the latest
progress report. Thus far, there is no standard or draft standard for
a Standard Upper Ontology (SUO) from this group. Instead, several draft
proposals have been made, one of the more developed suggestions of
which is SUMO. SUMO adopts a polytree architecture of categories, in
there are cases of multiple supercategories, for example, Group is a
subcategory of both Collection and Agent.
Its development may
have contributed to the multiplicative approach, as SUMO originates
from a merge of several top-level ontologies
(cf. (42)), including one of Russell and Norvig
(49), one of John Sowa
(54), as well as several others.
Similarly, Roberto Poli contributes an additional important account of ontology in the field of
computer science (44). In
particular, Poli presents a theory of ontological
levels (cf. (45,46)) that is acknowledged and adopted in GFO.
Apart from recent approaches to top-level ontologies, other fields
offer contributions as well. In particular, issues related to those
raised herein have been discussed in knowledge representation,
knowledge-based systems research as well as database and
object-oriented modeling. The focus in these areas may be a different
one, but often some ontological questions are touched as well.