Introduction to Expert Introduction to Expert Systems Systems Dr. Khaled Shaalan Prof. Dr. Ahmed Rafea Central Lab. For Agricultural Expert Central Lab. For Agricultural Expert Systems Systems
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Introduction to Expert Introduction to Expert SystemsSystems
Dr. Khaled ShaalanProf. Dr. Ahmed Rafea
Central Lab. For Agricultural Expert Central Lab. For Agricultural Expert SystemsSystems
Topics
• What is AI ?• What is KBS?• What is expert system?• The structure of an expert system• Characteristics of an expert system• When are expert systems useful?• The players in the expert system game • Evolution of expert systems
What is AI?
ARTIFICIAL INTELLIGENCE (AI) IS A BRANCH OF COMPUTER SCIENCE THAT IS STUDYING HOW TO LET COMPUTERS PERFORM FUNCTIONS CONSIDERED TO BE HIGH LEVEL HUMAN ACTIVITIES
What is KBS?
A KNOWLEDGE - BASED SYSTEM (KBS) IS A COMPUTER PROGRAMTHAT USES KNOWLEDGE AND PROBLEM SOLVING TECHNIQUES
What is expert system?
AN EXPERT SYSTEM (ES) IS A COMPUTER PROGRAM DESIGNED TO SIMULATE THE PROBLEM-SOLVING BEHAVIOR OF AN EXPERT IN A NARROW DOMAINOR DISCIPLINE.
What is expert system?(cont.)
ARTIFICIALINTELLIGENCE
PROGRAMS
Exhibit intelligentbehavior by skillful
application of heuristics
make domain knowledgeexplicit and separate from
the rest of the system
KNOWLEDGE-BASEDSYSTEMS
Apply expert knowledgeto difficult, real world
problems
EXPERTSYSTEMS
The structure of an expert system
KNOWLEDGE BASE Domain Knowledge
FACTS
RULES
INTERPRETER
SCHEDULER
Organizing KnowledgeEXPERT SYSTEM
INFERENCE ENGINE General
problem-solving knowledge
Representing knowledge
l Rule-based methodsl Frame-based methods
Rules
l A rule is a formal way of specifying a recommendation, directive, or advice
l A rule is expressed as IF IF premisepremise THEN THEN conclusionconclusion
orIF IF conditioncondition THEN THEN actionaction
A diagnostic ruleIFIF there are spots on leaves, and
the color of spots is paleyellow, gray, or purple, andthe shape of spots is bounded making acute angle with veins, and the season is spring
ThenThen the disease is downy mildew -probability = 0.9
A treatment ruleIFIF the disease is downy mildew
THENTHEN the treatment method is chemical spraying, and the material used isredomil+copper
Drawing inferences from rules
l Forward chainingl Backward chaining
Frames
l A frame is a description of an object that contains slots for all of the information associated with the object
l Slots may contain (default) values, or procedures by which values may be obtained
Soil FrameSlots FacetsPh value type: real
single/multiple: single possible value: > 0.0 & 14.0
EC value type: real single/multiple: single possible value: > 0.0
Texture value type: nominalsingle/multiple: singlepossible value: sand, loam, clay, heavy clay,gravely, coarse sand, silty clay, silty clayloam, salt loam, fine sand, sand clay loam,silt loam, sandy loam, loamy fine sand
… …
Frames connected by IS-A relation
Leaf mold
Downy mildew
Fungal
Mosaic
Green Mosaic
Viral
Disease
Spiders
Broad mite
Mites
Low temperature
Heavy irrigation
Environmental
aphids
Insect
Nitrogen
Iron
Nutrition Deficiency
Bromide
Bazamide
Toxicity
Root knot
Root lesion
Nematode
Disorder
Disorder hierarchy
generic
specialized
Drawing inferences from frames
l Inheritancel Procedure attachment
Characteristics of an expert system
Expert System
Expertise
Symbolic reasoning
Depth
Self-knowledge
Exhibit expert performanceHave high level of skillHave adequate robustnessRepresent knowledge symbolicallyReformulate symbolic knowledge
Handle difficult problem domainsUse complex rules
Examine its own reasoningExplain its operation
When are expert systems useful?
l Nature of the task– Experts can do better than nonexperts– The task involves reasoning and
knowledge, not intuitions or reflexes– The task can be done by a person in
minutes or hours– The task is concrete enough to codify– The task is commonly taught to novices
in the area
When are expert systems useful? (Cont.)
l Availability of knowledge– Recognized experts exist– There is general agreement among experts– Experts are able and willing to articulate the
way they approach problems
The players in the expert system game
Tool builder
EXPERTSYSTEM
BUILDINGTOOL
Domainexpert
Knowledgeengineer
EXPERTSYSTEM
ClericalStaff
End-user
Interviews
Buildsrefines
and tests
Extendsand test
Builds
Uses Uses
l Programming languagel Shell
Expert system building tool
Shells VS Programming languages
Features Shells Prog. Lang.
Ease & speed ofdevelopment
Higher Less
KB Structure&reasoning
Restricted bythe tool
May be developedAs needed
KB maintenance Easier Difficult
Shells VS Programming languages (Cont.)
Features Shells Prog. Lang.
Interfaces Not alwaysfriendly oravailable
Have to bedeveloped
Efficiency/Performance
Slower Faster
Explanation Restricted bythe tool
May be developedas needed
Evolution of expert systemsDevelopment Stage Description
DemonstrationPrototype
The system solves a portion of the problemundertaken, suggesting that the approach is viableand system development is achievable. (test ideas)
Researchprototype
The system displays credible performance on theentire problem but may be fragile due to incompletetesting and revision. (test cases)
Field prototype The system displays good performance with adequatereliability and has been revised based on extensivetesting in the user environment. (test real problems)
Production model The system exhibits high quality, reliable, fast, andefficient performance in the user environment.(extensive field tests)
Commercialsystem
The system is a production model being used on aregular commercial basis.
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