Information Technology Reference
In-Depth Information
example space intensively. Figure 9.1 illustrates the relationship among three
spaces.
Concept space refers to the set composed of all concepts that a learning
program can depict. Every point corresponds to a unique subset of example space.
For instance, C
1
corresponds to I
1
, I
2
and I
3
. However, one point in the concept
space corresponds to more points in concept description space, these points can
be divided into two categories: operational and non-operational. Here, C
1
corresponds to D
1
(non-operational description) and D
2
(operational description).
Two descriptions correspond to the same concept are called synonymy. A case in
point is that D
1
and D
2
are synonymy. The task of EBL is to transfer the
non-operational descriptions into operational descriptions.
Concept description space
Concept space
Instance space
D
1
non-operational
I
1
C
1
I
2
operational
I
3
D
2
Figure 9.1. Space description of EBL
As shown in figure 9.1, D
1
is the initial and non-operational description
submitted to the system and D
2
is the learned final, operational description.
Therefore, D
1
can be regarded as the starting point for searching while D
2
is the
solution point. The explanation is just transformation of space and operable is the
criterion for halt of searching. Concept operational is defined as the
transformation from D
1
to D
2
(Keller, 1987).
From the concept's point of view, each EBL system is made up of operational
evaluation process, description of appraisal concept and generation of operational
evaluation results. The three dimension characteristics generated from the
evaluation process include variability, granularity and certainty. Table 9.1 shows
the characteristics of operationality of several systems.
