Expert Systems: Rule-based reasoning 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, the domain knowledge is represented by
a set of IF-THEN production rules
In a rule-based expert system, the main difference between a database and a knowledge base is that
a databased contains facts and a knowledge base contains rules
What is forward chaining?
A data-driven reasoning. A technique for gathering information and then inferring from it whatever can be inferred
How does forward chaining work?
starts with the available data and uses inference rules to extract more data until a goal is reached. The inference engine searches the inference rules until it finds one where the antecedent is true. When a rule is found, the engine can conclude the consequent, adding new information to its data. Inference engines will iterate through this process until a goal is reached
What is backward chaining?
Backward chaining is the goal-driven reasoning. An expert system has a goal, and the inference engine attempts to find the evidence to prove it.
What is metaknowledge?
Knowledge about the use and control of domain knowledge
The inference engine compares each ______ stored in the knowledge base with ______ contained in the database.
rule, facts
When the IF part of the rule matches a fact, the rule is ______ and its THEN part is ______
fired, executed
In the forward chaining, each time only the _____ rule is executed. When fired, the rule adds a new ______ in the database. The match-fire cycle ______ when no further rules can be fired.
topmost, fact, stops
An inference engine backchains by determining the highest _____ goal from user _______, then asking questions about rules in order to find or rules that lead to _______.
priority, specifications, the goal
The problem with forward chaining
Many rules executed 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 to choose between forward and backward chaining?
Choose forward chaining if an expert needs to gather information first and then tries to infer from it. Choose backward chaining if the expert begins with a hypothetical solution and then attempts to find facts to prove it
What is conflict resolution?
A method for choosing a rule to fire when more than one rule can be fired in a given cycle
3 methods used for conflict resolution
Fire the rule with the highest priority. Fire the most specific rule. Fire the rule that uses the data most recently entered in the database.
