About Expert systems(basics)

                 
                

Expert Systems
Contents:    
       I.            History of ES
    II.            General concept
 III.            Basic Types
IV.            General stages
   V.            Characteristics
VI.            The advantages and limitations
VII.            ES categories and examples
  I. History of ES
 
1.      Early 1960
o   AI research was dominated by a believe that:
A few laws of reasoning + powerful computers = expert or even superhuman performance.
o   General-purpose Problem Solver (GPS):
a. A procedure developed by Newell & Simon, includes:
1. A set of operators
2. Preconditions
3. Post conditions
4. Heuristic for operators to try first
b. Tries to work out the steps needed to change a certain initial situation into a desired goal.
o   On this time, concentration is on problem-solving mechanism.
·        4
2.      Mid-1960s
o   There were special types of AI program to successfully deal with complex problem in a narrow domain:
a.     Dendral (E. Feigenbaum, Standford Univ.)
b.     MYCIN
o   General purpose to special-purpose programs.
o   Recognized that the problem-solving mechanism is only a small part of a complete intelligent computer system.
3.     5
3.     Mid-1970s
o   Several ES had begun to emerge.
o   “Knowledge” becomes target of study.
o   Development of knowledge representation theories.
o   Key insight:
The power of an ES is derived from the specific knowledge it possess, not from the particular formalisms and inference schemes it employs.
4.     6


4.      Beginning of the 1980s
o   Commercial applications were built, such as:
a.     XCON & XSEL (at DEC)
b.     CATS-1 (at General Electric)
o   Effort to develop tools for speeding up the construction of ES, such as:
a.     EMYCIN
b.     AGE
5.     1983
o   Some tools become commercially available.
o   Most of the early development tools required special hardware, e.g.  LISP machine.
6.     Late 1980s
o   Development software can run on regular computers including microcomputers.
7.     Now(At Present)
o   ES is used in many fields.
     Expert System
1st developed: Contain human expert knowledge exclusively.
NOW :
a.     Any system that uses ES technology.
b.     The knowledge: Expertise’s + available knowledge generally.
8.     9
II. General Concept of Expert System

The modern ES is a convergence of 3 important factors:




 Notes:
 The process is mimic human expert when they solve a specific problem.

Knowledge base:
o   There are some knowledge representations.
o   But the common methods of representing knowledge are -
 IF - THEN type rules and frame.
     Inference Engine:
o   There are a lot of algorithm can be used in AI.
o   But ES is using algorithm that mimics human thinking which are forward chaining and backward chaining.

   Conventional System vs Expert System

              
             
III.           Basic Types of ES
o   Stand-alone: When the computer is running a program, it is totally dedicated to it.
o   Embedded: The ES is just a portion of another larger program.
  
 Type of embedded expert system:
              

IV.           General Stages of ES Development

     General Stages in the development of an Expert System.
                 
V.               Characteristics
High performance:
 The response at a level of competency equal to or better than an expert.
Adequate response time:
 Perform in a reasonable time, comparable to or better than previous time.
Good reliability:
Must be reliable and not prone to crashes or else it will not be used.
     Understandable:
  Have an explanation capability.
  a. Sanity check
  b. Accuracy validation of the knowledge
Flexibility:
Important to have an efficient mechanism for adding, changing, and    deleting knowledge.




VI.           A. Advantages of Expert System
Increased availability:
Expertise is available on any suitable computer hardware.
     Reduced cost:
The cost of providing expertise per user is greatly lowered.
     Reduced danger:
Can be used in environments that might to hazards for a human.
    Permanence:
The knowledge will last indefinitely.
    Multiple expertise’s:
·        The knowledge of multiple experts can be made available to work simultaneously & continuously on a problem at any time of day or night.
·        The level of expertise may exceed that of a single human expert (HE).
    Increased reliability:
·        Increase confidence by providing a 2nd opinion.
·        When HE/SHE is tired or under stress HE/SHE will make mistake.
    Explanation:
·        Can explain in detail the reasoning that lead to a conclusion.
·        A human may be too tired, unwilling, or unable to do this all the time.
    Fast response:
·        May response faster and be more reliable.
·        Real-time ES: emergency situations.
   Intelligent tutor:
·        Letting the student run sample programs & explaining the system’s reasoning.
VII.        B. Limitations of Expert System:
1. Not easy to do rule induction (system creates rules from data).
o   Especially when the knowledge has never been explored.
o   Inconsistencies, ambiguities, duplication, etc.
2.     Lack of causal knowledge
o   ES do not really have an understanding of the underlying causes & effects in a system.
o   Using shallow knowledge, than deep knowledge.

3.     ES expertise is limited to the knowledge domain contained in the system.
4.     ES cannot generalize their knowledge by using analogy to reason about new situations the way people can.
5.     Knowledge acquisition bottleneck:
Repeating the cycle of interviewing the expert, constructing a prototype, testing, interviewing, and so on.






VII.Categories of  ES:
   Generic ES categories:
– Interpretation : clarification of situations.
– Design : developing products to specification.
– Planning : developing goal-oriented schemes.
– Prediction : intelligent guessing of outcomes.
– Diagnosis : estimate defects.
– Repair : automatic diagnosis, debugging, planning and fixing.
– Control : intelligent automation.
– Instruction : optimized computer instruction.

      

                       

                       
                     

                 

                  


                 

                 

                  

                   

                   

                   

                 

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