CSCI3406 Fuzzy Logic and Knowledge Based Systems AI

1
CSCI3406 Fuzzy Logic and Knowledge Based Systems
(AI)

• Tutorial
• KBS in Business (a video)
• Example for Backward Chaining

2
KBS in Business (a video)

• We will be watching a video on Expert systems
  for business benefit
• We will be discussing the following issues before
  and after the video
• Where the KBS/ES has been used
• What benefits have been mentioned
• If any difficulties or disadvantages are
  discussed?

If you wish, you can borrow the video from the
main library Expert systems for business
benefit Videorecording, Video 006.33/EXP In
addition, you may look at the followings 1.
Expert systems Videorecording techniques and
applications. - Video 1 The automation of
expertise / Jim Alty, Video L 006.33/ALT 2.
Expert systems videorecording automating
knowledge acquisition / by Donald Michie and
Ivan Bratko, Video 006.33/MIC 3. Professional
judgment Videorecording Knowledge based
systems, Video WD321\4
3

• Tutorial Forward Backward Chaining
• Suppose the following rules and facts are given
• Rule 1 if A and B and C then D
• Rule 2 if A and E then C
• Rule 3 if B and C then A
• Rule 4 if C and E then B
• Fact 1 E is true
• Fact 2 A is true
•  
• 1. With reference to the above example rules and
  facts, show how D can be proved true by backward
  chaining
• 2. Suppose the truth-value of E is unknown during
  a backward chaining inference process. The system
  may ask the user for its value. Explain briefly
  the response of this expert system if the user
  asks the question why is the truth-value of E
  required?

4

• Answer 1
• Goal D
• Truth-value of D unknown
• Only one rule has D as a conclusion Rule 1
• Set up sub-goals A and B and C (antecedents) to
  replace D goals are A,B,C
• Now goal is A
• Fact 2 is A is true
• Unstuck goal new goal is B goals are B, C
• New goal is B
• B truth-value is not known
• Only 1 rule has B as a conclusion - Rule 4
• Set up sub-goals C and E (antecedents) goals
  are C, E, C
• New goal is C
• C truth-value is unknown
• Only 1 rule has C as a conclusion Rule 2
• Set up sub-goals A and E (antecedents) goals
  are A, E,E,C
• New goal is A
• Fact 1 A is true un-stack A goals are E, E,
  C
• New goals is E

• Answer 2
• In backward chaining the system has a goal stack
  and a record of the rules applied. This can be
  used to tell the user why he/she us being asked
  for a truth-value. In this case, the response
  would be because I am trying to prove that C is
  true using Rule 2 if A and E then C and I know
  that A is true (Fact 2).