SEKE 2012 Proceedings - Knowledge Systems Institute

information in a clear visual model that can be manipulated
for multiple views.
This paper is organized as follows. Section 2 presents
relevant background literature about the field of ontology
editors, ontology visualization tools and the structure of 3D
graphic rendering. Section 3 describes the development of
the proposed ontology 3D v isualization tool. Section 4
presents the application of Onto3DViz on ontology
visualization of the CO 2 capture process system, and
section 5 discusses some strengths and weaknesses of the
tool for ontology visualizing application. Section 6
provides a conclusion and some discussion of future work.
II. BACKGROUND LITERATURE
A. Inferential Modeling Technique (IMT)
The IMT supports “an iterative-refinement of
knowledge elements in a problem-domain that provides
top-down guidance on the knowledge types required for
problem solving” [2]. Typically, the resulting inferential
model consists of th e four levels of knowledge: domain
knowledge, inference knowledge, task knowledge and
strategy knowledge. The domain knowledge, also referred
as static knowledge, consists of concepts, attributes, values
and their relationships; the task knowledge, also referred as
dynamic knowledge, includes objectives, tasks, and
relationships among objectives and tasks. Static a nd
dynamic knowledge are in tertwined in that a tas k is a
process that manipulates static knowledge to ac hieve an
objective. T he details of this modeling technique can be
found in [2].
B. Ontological Engineering Modeling Tools
There are v arious modeling tools available that support
ontological engineering. Some examples include KAON
[4], OntoStudio [5], Protégé [6] and Dyna [1]. KAON is an
open source ontology management infrastructure, which
supports creation, storage, retrieval and maintenance of an
application ontology. KANO is based on the RDFS file
format. The successor of KANO, called KANO2, supports
OWL and F-Logic. OntoStudio is a co mmercial ontology
modeling tool, which supports the creation and
maintenance of application ontologies. OntoStudio
supports a variety of file formats, such as F-Logic, OWL,
RDF(S) and OXML (OntoStudio’s own XML format).
Protégé is another open source ontology editor and
knowledge-based framework, which supports frame based
(F-Logic) and OW L based on tology modeling. Protégé
ontologies can be exported into a v ariety of formats
including OWL, RDF(S), and XML schema. Protégé has
been designed so that more features can be added to it by
means of implemented plug-ins. For exa mple, Dyna has
been implemented as a Protégé-OWL editor plug-in that
addresses the need for dynamic knowledge modeling. Dyna
supports ontologies represented in the XML or O WL
languages format.
C. Ontology Visualization Tools
There are many ontology visualization tools. Although
Protégé has some degree of visualization capabilities, the
actual ontology visualization applications are implemented
in its plug-ins. Some examples of these ontology
visualization plug-ins include Jambalaya [7] and
OntoSphere [8].
Jambalaya provides several viewing perspectives for
the ontology model and supports operations such as
filtering and searching, so that th e user can examine and
interact with the knowledge elements at different levels of
abstraction and detail s. However, Jambalaya only
visualizes the static knowledge of classes and instances of
an application ontology, it does n ot support dynamic
knowledge visualization. Furthermore, since Jambalaya is
based on 2D graphics, the space it supports is insufficient
for rendering complex knowledge. In its representation,
text labels and s ymbols tend to ov erlap when the domain
ontology includes a hierarchy of many levels of concepts.
This deficiency means it is diff icult for users to view and
understand the concepts and the relationships among
concepts when the domain ontology is complex.
OntoSphere is the only existing ontology visualization
tool that adopts the 3D view, thereby extending the volume
of space available for visualizing overcrowded concepts. A
main advantage of a 3D rep resentation is that it a llows
users to manipulate the visualized knowledge elements of
the application ontology by means of the actions of
zooming, rotating and translating. Through physical
manipulation of the concepts, the user can better
understand a co mplex ontology. For t his purpose,
OntoSphere provides four scenes so that the user can
observe a v isualized application ontology from multiple
perspectives. However, OnotoShere had not been
developed based on any ontological engineering
methodology, and it does not support visualization of
dynamic knowledge. Although the employment of 3D
graphics enlarges the space availab le for OntoShpere in
rendering images, the problem of overlapping concepts and
labels can still occur when the ap plication ontology to be
visualized is complex.
III. DESIGN AND IMPLEMENTATION OF
ONTO3DVIZ
A. Overview
Onto3DViz has been developed for visualizing an
application ontology in 3D graphics. It is written in Java
language and its 3D visualization engine is implemented in
java 3D. The main difference between Onto3DViz and
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