1.1 Expert System
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Transcript of 1.1 Expert System
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Expert System
An EXPERT SYSTEM is a computerprogram that exhibits Expert Levelperformance in solving complex
problems.
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Reasons with Facts about the World:
Combines General Facts/Rules (about Diseases, ...)
with Specific Facts (about Patient)
to Produce new Conclusion (diagnosis)
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Story
MD sees patient perhaps MENINGITIS! Performs standard tests
Calls Infection Disease (medical) expert
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Dialogue: Expert asks for info re: patient
Fever, Organism Morphology, Gram Stain, Spinal Fluid,
Doctor's answers: D IRECT : from direct measurement, Lab tests Qua l i t a t i v e : Has HIGHfever Vague : Portal of Entry was GastroIntestinal (w/certainty 0.6) Un k n own : dont know identity of organism?
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Story cont
MD can ask questions: Why ask about portal of entry? Expert answers:
trying to showinfecting organism is ENTEROBACTERICAE
this information is crucial in that decision. If further questioned, point to definitive study
Expert provides DIAGNOSIS organism was one of {E.coli, Enterobacteria } suggest TREATMENT: Give GENTAMICIN
Happily ever after...
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The Catch
Expert System
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Medical Expert Systems
MYCIN
Blood Infections
CADUCEUS
Internal Medicine CASNET
Glaucoma
Present lllnessProgram
Kidney
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Digitalis advisor Erratic Heartbeat
VM
Ventilator Management ALVEN Ventricle Movement
ONCOCIN
Cancer TreatmentProtocols
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Declarative Programming''
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Knowledge Base
--- -- --- ---- --- - -- ---- - --- ------ -- --- --Facts about the world
-- ---- --- ---- ----- -- ----- -- ----- -- --- - -
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Is true?
ProofProcedure
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Yes No
Give Gentamycin?
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Advantages of Framework
Simply
Information is Modular
Easy to Build
Easy to Modify (Extend, Debug)
Capable of Explanation
Declarative
Re-use same info for different tasks
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store truthsask for other truths
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Computers ManipulateSYMBOLS
Numbers
3, 5, ...
Addition, Multiplication, ...
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PropositionsD1 is an inverter''
Inverters flip bits''... Deduction, ...
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Simple Deduction
Socrates is a man.
If Socrates is a man,Then Socrates is mortal.
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Socrates is mortal.
In general
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Example of Deduction
RULES FACTS
R1:IfSocrates is a Man,
Then Socrates is Mortal
o
o
o
F1: Socrates is a Man.
o o10
Socrates is Mortal(Goal)
Socrates is a Man(NewGoal)
R1
Knowled
geBa
se
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Example of Deduction, #2
RULES FACTS
R1:IfPlato is a Man,Then Plato is Mortal
R2:IfPlato is a Cat
Then Plato is Mortal.
R3:IfPlato purrs,
ThenPlato is a Cat.
oo
F3: Plato purrs.
o
o
o 11
Plato is Mortal
Plato is a Man
R1
Plato is a Cat
R2
Plato purrs
R3
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Example of Deduction, #3
RULES FACTS
R2:IfPlato is a Cat
Then Plato is Mortal. o
R9:IfAristotle is a human and Aristotle is male,
ThenAristotleis a man
o
o
o
F3:Aristotleis male.
o
F8:Aristotle is a human
o 12
Aristotle is a man
Aristotle is maleAristotleis a Human
R9
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Oversimplified Proof Process
1. If Goal = FACT
then DONE YES
Else
1. Goal = Then Part of Rule R
then Goal If Part ofR
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i
ii+1
else DONE NO
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JustManipulating Symbols
Consider claim
This is Belgium.
based on proof
Today is Tuesday. If Today is Tuesday
Then This is Belgium.
This is Belgium
Conclusion iswrong!
Conclusion isONLY AS TRUE
as PREMISES
If Premises true,then Conclusion is.
Not fault of PROOFprocess
GIGO14
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Rules
R1: if(1) You have a Parking Permit & (2) This space is Permit-Parkable,
then You can park at this space.
R2: if(1) This space is a Parking Space & (2) Permit-Sign at this space &
(3) Current date is Acceptable,then This space is Permit-Parkable.
R3: if(1) Current time is 7am-Midnight & (2) This space is Permit-Parkable,
then You can park at this space.
R4: if (1) Current month is Dec-Mar,then Current date is Acceptable.
R5: if (1) Current month is in Apr-Nov &
(2) Current day of month is 15then Current date is Acceptable.15
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Facts
This space is a Parking Space. You live near this space. You have a Parking Permit.
Current month is in Apr-Nov. Current day is Tuesday. Current day of month is 15. Permit-Sign at this space.
You own a car. Your car is >5 years old. Current time is 3am. You have $18.00. ... 16
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Inference Graph
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You can park at this space
You have a Parking Permit This space is Permit-Parkable
Parking Space
Permit-Sign
Current date is Acceptable
15Apr-Nov
R1
R2
R5
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Additional Rules
R1: if(1) You have a Parking Permit & (2) This space is Permit-Parkable,
then You can park at this space.
R2: if(1) This space is a Parking Space&
(2) Permit-Sign at this space &
(3) Current date is Acceptable,then This space is Permit-Parkable.
R3: if(1) Current time is 7am-Midnight&
(2) This space is Permit-Parkable,then You can park at this space.
R4: if (1) Current month is Dec-Mar,then Current date is Acceptable.
R5: if (1) Current month is in Apr-Nov&
(2) Current day of month is 15then Current date is Acceptable.
R7: if (1) You live near thisspace &
(2) You own a car & (3) You apply for a permit,
then You have a ParkingPermit.
R8: if (1) You can park at thisspacethen You can take a car.
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Inference Graph
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You can park at this space
You have a Parking Permit This space is Permit-Parkable
Parking Space
Permit-Sign
Current date is Acceptable
15Apr-Nov
You can take a car
live near
own a car
apply for permit
R7
R8
R1
R2
R5
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Mycin: What is the suspected portal of entry of ORGANISM-1 into this sterile site?
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Doctor: WHY
Mycin: [ie, why is it important to determine the site?]
[3.0] to determine which organism(s) to cover
It has already been established that
3.1] site of culture is blood
3.2] organism stain is gram positive
Therefore, if
3.3] portal of entry is g.i.
3.4] locus of infection is Pelvis or Abdomen,Then
strongly suggestive evidence (0.9) that therapy
should cover enterobacteriaceae.
[Rule 095]. . .
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Mycin: What is the suspected portal of entry of ORGANISM-1 into this sterile site?
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Doctor: WHY
Mycin: [ie, why is it important to determine the site?]
[3.0] to determine which organism(s) to cover
Ifhas already been established that
3.1] site of culture is blood
3.2] organism stain is gram positive
Therefore, if
3.3] portal of entry is g.i.
3.4] locus of infection is Pelvis or Abdomen,Then
strongly suggestive evidence (0.9) that therapy
should cover enterobacteriaceae.
[Rule 095]. . .
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Advantage of RuleTransparency
Explain reasoning
Support / Credability
Helpful when building/extending system
modifying system
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Issues
Faster Computation
User Interaction
Focus of Attention
Human Engineering
Variables
Control of Search Which (sub)goal? Which rule?
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Research Issues
Better Decision Making
Coping with Uncertainty
Better Explanation
Deeper Knowledge
First Principles
Meta
Acquiring the Knowledge
from expert
from data24