Information Technology Reference
In-Depth Information
From Fig. 13.6, if a MOVING node is labeled by detector d
1
, then the
directed arc from MOVING to ALERT can be built by the following classifier:
00#############1 / 01001###########
The directed arc from SMALLNOT STRIPED and ALERT to TARGET
then can be built by a single classifier:
00########00####01001########### /
10001###########.
The other part in the network can be similarly accomplished.
13.5 Bucket Brigade Algorithm
A classifier system is a highly time-parallel learning system based on rules. It can
continuously build and improve its environmental model, which is built by using
obtained experience. The basic units of classifier system consists of message and
classifier(rules). However, the combination of the two units and default classifier
can generate very complex knowledge structure.
Two kinds of learning mechanism are used in classifier system:
(1) Bucket brigade algorithm. According to the contribution to the system, every
rule is assigned with a credit value.
(2) Algorithm for discovering rules. This kind of algorithm may include genetic
algorithm, which can discover new rules, so as to improve system's
knowledge database.
Based on the whole availability of classifier system, bucket brigade algorithm
endows the classifier with a credit value. By modifying executing cycle,
competition mechanism is used in bucket brigade algorithm. In the working cycle,
each classifier scans all messages in global message table. Each message
satisfying condition can generate new messages. By modifying this process, the
satisfied classifier must use competition mechanism to obtain messages from
message table. Each classifier bids based on intensity, and only the classifier with
higher bidding scale will obtain message from message table. Bidding scale is
related not only to the intensity of classifier but also to its characteristics. More
precisely, bidding scale is directly proportional to the product of the intensity and
the characteristic. If condition part of classifier C is satisfied, bidding scale can
be expressed in the following form:
Bid(
C
t
) =
cR
(
C
)S(
C
t
)
(13.14)
