Decision Support Tools for Ontological Engineering - Efficient Decision Support Systems: Practice and Challenges from Current to Future - page 58

3.1.5 Positioning of visual objects
Every 3D system requires a set of 3D coordinates to define its position and orientation. The
3D coordinate system used in Onto3DViz is defined as shown in figure 3.
This definition of the 3D coordinates in Onto3DViz is commonly adopted in most 3D
computer graphic languages. The X axis is a horizontal line on a flat piece of paper, going
from left to right, and the numbering goes from negative on the left to positive on the right.
The Y axis is a vertical line on a piece of paper, and the numbering goes from negative in the
bottom to positive at the top. The Z axis is perpendicular or orthogonal to the piece of paper,
and the numbering follows the direction that is pointing out from the surface of the piece of
paper. The intersection of these three axes is the origin. Onto3DViz allocates visual objects
into three X-Y planes along the Z axis. They are:
 Class plane: this is the first X-Y plane located at the positive region of the Z axis as
shown in figure 4a. The visual objects of classes are placed on this plane.
 Instance plane: this is the second X-Y plane located at the origin of the Z axis as shown
in figure 4b. The visual objects of instances are located on this plane. If there is no
instance being created in the ontology, this plane is not visible in the 3D model.
 Objective and task plane: This X-Y plane is perpendicular to and located in the negative
region of the Z axis as shown in figure 4c. This plane contains the dynamic knowledge
elements. The objectives are placed at the top region of this vertical plane, and the tasks
associated with the objectives are placed in the bottom region of this plane. If there is
not any dynamic knowledge element in the ontology, this plane is not visible in the 3D
model.
The technique of organizing the placement of knowledge concepts at multiple levels in the
three dimensional space enables categorization according to the types of the knowledge
concepts, but also solves the problem of concepts being overcrowded in a shared space.
Fig. 3. The 3D coordinate system of Onto3DViz