CS62S: Expert Systems

1
CS62S Expert Systems

• Based on
• The Engineering of Knowledge-based Systems
  Theory and Practice
• A. J. Gonzalez and D. D. Dankel

2
Introduction to Knowledge-based Systems

• General problem solving knowledge
• Intelligent program
• Inference engine
• Knowledge base
• Data / Fact base
• Separation of knowledge from its use
• For a new problem domain change knowledge base

3
Knowledge Representation

• Logic
• Rules
• Associative (semantic) networks
• Frames
• Objects

4
Traditional Computer Programming

• Structured sequence of steps
• Algorithm
• Finite amount of time

5
Search alternative to algorithmic solution

• Path connecting problem to the solution
• Problem space
• Procedurally defined
• Network
• Tree
• Solution space (problem space examined)

6
Search Methods

• Random
• Blind
• Directed

7
Search Types

• Depth-first
• Breath-first
• Beam
• Hill-climbing
• Branch and bound
• Best-first
• A (best-first and branch and bound)

8
Heuristics vs. algorithm

• Specific knowledge
• Rule of thumb
• Prior knowledge
• Expertise
• Timely solution
• Estimation

9
Gonzalez and Dankel describes knowledge-based
systems as

• A computerized system that uses knowledge about
  some domain to arrive at a solution to a problem
  from that domain. This solution is essentially
  the same as that concluded by a person
  knowledgeable about the domain of the problem
  when confronted with the same problem

10
Expert systems

• Separation of knowledge from how it is used
• Use of highly specific domain knowledge
• Heuristic rather than algorithms

11
MYCIN

• Used to diagnose blood disorder
• Incorporates all three elements

12
Types of expertise

• Associational
• The internal workings of a system are not
  understood. The behaviour is used to solve
  problems

13

• Motor skills expertise
• Practice makes perfect (sports, physical tasks,
  etc)

14

• Theoretical expertise
• The internal workings of a device or system are
  well understood. The expert can solve problems
  never seen before.

15
Advantages of Expert Systems

• Wide distribution of scarce expertise
• Ease of modification
• Consistency of answers
• Perpetual accessibility
• Preservation of expertise
• Solution of Problem involving incomplete data
• Explanation of solution

16
Disadvantages

• Answers may not always be correct
• Knowledge limited to the domain of expertise
• Lack of common sense

17
Expert systems architecture

• User
• Knowledge engineer
• Tool builder

18
(No Transcript)
19
(No Transcript)
20
(No Transcript)