Lab 2(expert systems -2) Flashcards
What is the technique of establishing the facts from the knowledge base of an expert system to prove a given goal?
Backward chaining
In a rule-based expert system, how is the domain knowledge represented?
A set of IF-THEN production rules
In a rule-based expert system, what is the main difference between a database and a knowledge base?
a database contains facts and a knowledge base contains rules
How is forward chaining driven?
Forward chaining is the data-driven reasoning.
One fact about a rule?
Any rule can be executed only once
What is Forward chaining ?
Forward chaining is a technique for gathering information and then inferring from it whatever can be inferred
How is backward chaining driven?
Backward chaining is the goal-driven reasoning.
Is the order of rules important in an expert system?
The order of the rules is not important in an expert system.
In an expert system, metaknowledge is knowledge
about what?
the use and control of domain knowledge
In an expert system, the knowledge and its processing are
linked
Inference engine
The inference engine compares each rule stored in the knowledge base with facts contained in the database.
Rules (IF-THEN)
When the IF (condition) part of the rule matches a fact, the rule is fired and it’s THEN (action) part is executed
What happens in Forward chaining?
In the forward chaining, each time only the topmost rule is executed. When fired, the rule adds a new fact in the database. The match-fire cycle stops when no further rules can be fired.
How does an inference engine backchain?
An inference engine backchains by determining the highest priority goal from user specifications, then asking questions about rules in order to find a rule or rules that lead to the goal
Briefly discuss the problem with forward chaining?
In forward chaining, many rules may be executed that have nothing to do with the established goal. Therefore, if our goal is to infer only one particular fact, the forward chaining inference technique would not be efficient.
How do you choose between forward and backward chaining?
If an expert first needs to gather some information and then tries to infer from it whatever can be inferred, choose the forward chaining inference engine. However, if your expert begins with a hypothetical solution and then attempts to find facts to prove it, choose the backward chaining inference engine.
In an expert system, one method used for conflict resolution is to fire the rule with the highest priority. List other two methods and explain the way these methods work:
1) Fire the most specific rule. It is based on the assumption that a specific rule processes more information than a general one.
2) Fire the rule that uses the data most recently entered in the database. This method relies on time tags attached to each fact in the database. In the conflict set, the expert system first fires the rule whose antecedent uses the data most recently added to the database.
