What is an Expert System? An Expert System is a computer system that emulates the decision-making ability of a human expert.
Expert systems are designed to solve complex problems by reasoning about knowledge, like an expert.
CONT…Expert systems are:
Knowledge based systemsPart of the Artificial Intelligence field
Computer programs that contain some subject-specific knowledge of one or more human experts
Systems that utilize reasoning capabilities and draw conclusions.
4 Major ComponentsEvery expert system consists of four
principal parts
The rule base or knowledge baseWorking storageThe inference engineUser interface
1) The rule base or knowledge baseThe knowledge base is the
collection of facts and rules which describe all the knowledge about the problem domain
Contain everything necessary for understanding, formulating and solving a problem.
Stores all relevant information, data, rules, cases, and relationships used by the expert system
2) WORKING MEMORY (SHORT TERM MEMORY) Contains facts about a problem that
are discovered during consultation with the expert system.
System matches this information with knowledge contained in the knowledge base to infer new facts.
The conclusion reach will enter the working memory.
3) The inference engineThe inference engine is the part of the
system that chooses which facts and rules to apply when trying to solve the user’s query.
It taps the knowledge base and working memory to derive new information and solve problems
The inference engine is a computer program designed to produce reasoning on rules
It is based on logic
4) THE USER INTERFACEThe user interface is the part of the system
which takes in the user’s query in a readable form and passes it to the inference engine. It then displays the results to the user.
The user communicates with the expert system through the user interface.
It allows the user to query the system, supply information and receive advice.
The aims are to provide the same form of communication facilities provided by the expert.
The code that controls the dialog between the user and the system
Graphical ViewKnowledge Base
Domain Knowledge
Inference Engine
UserCase FactsConclusion
Working MemoryCase/Inferred Facts
Conclusion
Rule-based Systems Knowledge represented by series of rules
Frame-based Systems Knowledge represented by frames
Hybrid Systems Several approaches are combined, usually rules and
framesModel-based Systems
Models simulate structure and functions of systemsOff-the-shelf Systems
Ready made packages for general useCustom-made Systems
Meet specific need
Types of Expert Systems
ComparisonIssues Human Expert Expert System
Availability Limited Always
Geographic location
Locally available Anywhere
Durability Depends on individual
Non-perishable
Performance Variable High
Speed Variable High
Cost High Low
Learning Ability Variable/High Low
Explanation Variable Exact
AdvantagesQuick availability Reduce employee training costsReduce the time needed to solve problems.Combine multiple human expert intelligencesReduce the amount of human errors.Never "forgets" to ask a question, Ability to solve complex problemsConsistent answers for repetitive decisions, processes and
tasksExcellent PerformanceProvide ExplanationFast response
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