Artificial Intelligence and Soft Computing: Behavioral ... - Arteimi.info

ules supports the incremental development of reasoning systems by adding,
updating and deleting rules without affecting the existing rules in the
knowledge base.
3.11.4 Tracing of Explanation
A production system with conflict resolution strategy selects only one rule at
each recognize-act cycle for firing. Thus the fired rules are virtually timetagged.
Since the rules cause state-transition in a production system, stating
the rule to the user during its firing, let the user understand the significance of
the state transition. Presenting the set of the time-tagged rule in sequence thus
gives the user an explanation of the sequence of the operators used to reach the
goal.
3.12 Knowledge Base Optimization
in a Production System
The performance of a production system depends largely on the organization of
its knowledge base. The inferences derived by a production system per unit
time, also called time efficiency, can be improved by reducing the matching
time of the antecedents of the production rules with data in the WM. Further,
if the rules are constructed in a manner so that there is no conflict in the order
of rule firing, then the problem of conflict resolution too can be avoided.
Another important issue of rule-base design is to select the rules so that the
resulting state-space for rule firing does not contain any cycles. The last issue
is to identify the concurrently firable rules that do not have conflict in their
action parts. This, if realized for a rule-based system, will improve the
performance to a high extent. This issue will be covered in detail in chapter 22,
where the architecture of knowledge-based systems is highlighted.
For optimization of rules in a rule-based system, Zupan [9] suggested the
following points.
i) Construct by backward reasoning a state-space graph from the desired
goal nodes (states) up to the nodes, which cannot be expanded further in a
backward manner. Each goal node, also called fixed points, is thus
reachable (has connectivity) from all possible starting states. It may be
noted that some of the connectivity from the starting nodes to the goal
nodes may pass through cycles. It should also be noted that the resulting
state-space will not miss the shortest paths from the goal to any other