A computing system capable of representing and reasoning about some knowledge rich domain, which usually requires a human expert, with a view toward solving problems and/or giving advice. Such systems are capable of explaining their reasoning.
Does not have a psychological model of how the expert thinks, but a model of the expert’s model of the domain.
Expertise consists of those characteristics, skills and knowledge of a person (that is, expert) or of a system, which distinguish experts from novices and less experienced people.
often outperforming human beings at particular tasks are generally termed as expert.
Distinction Between an Expert System and a Knowledge-Based System
To be classified as an ‘expert system’ the system must be able to explain the reasoning process.
This is often accomplished by displaying the rules that were applied to reach a conclusion.
Rule-Based Expert Systems: Suitable Domains
No Unifying Theorem
Knowledge can be easily separated from the way it is used
Updating the knowledge base has to be easy
The knowledge base can be the only [indirect] communication channel among rules
Clinical/psychological and other domains, rather than mathematical/physical domains
MYCIN: The Problem
Roberts & Visconti :
Only 13% of patients are treated rationally
66% are being given irrational treatment
21% are being given questionable treatment
Irrationality means, for example:
Using a contra-indicated combination
Using the wrong agent for a specific organism
Not taking the required cultures
Program must be competent & easy to use
Must handle a large, changing body of knowledge
Interact with human users
Must take time into account
Work with incomplete or uncertain information
Translates rule to English before display
Rule acquisition/modification system
Expert System Structure User Interface Environment Language/Shell Explanation Facility Inference Engine Knowledge Base Blackboard
Stages in Diagnosis and Treatment
Decide if there is a significant infection
Identify the causing organism(s) by clinical and laboratory evidence
Decide what antibiotic agent the organisms are sensitive to
Prescribe the optimal drug combination for the particular case
A MYCIN Runtime Example
The MYCIN Architecture Consultation program Explanation program Knowledge-acquisition program Dynamic patient data Static factual & judgmental knowledge Physician user Infectious diseases expert