CIS4330: Professor KirsExpert Systems Slide 1 An Overview of Expert Systems.
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Transcript of CIS4330: Professor KirsExpert Systems Slide 1 An Overview of Expert Systems.
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CIS4330: Professor Kirs Expert Systems Slide 1
An Overview of Expert Systems
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CIS4330: Professor Kirs Expert Systems Slide 2
TOPICSTOPICS The nature of expertise
• Who is an Expert, and Why?
The Characteristics of an Expert Systems
• What Makes it different and Why ?
Additional Issues in Expert Systems
• Knowledge acquisition (Building knowledge bases)• Knowledge assessment• Explanation facilities
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CIS4330: Professor Kirs Expert Systems Slide 3
The Nature of Expertise Assumes a highly specialized
set of Skills• NOT just general knowledge
Assumes a very specialized problem domain
• Analogous to our previous ‘Forest vs. Tree’ Idea
Assumes logic, problem solving and experience
• NOT simple intuition or indefinable behaviors
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CIS4330: Professor Kirs Expert Systems Slide 4
The Nature of Expertise Who is an Expert??
• That is NOT an easy Question• There are many practitioner but
very few experts
Performance
Expertise
• Notice that just because you have experience, that does NOT mean that you are an expert
Characteristics of Experts• Fast, ACCURATE, problem Solving• Pattern Recognition• Use of Heuristics – Based on past
experience• Scarcity
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CIS4330: Professor Kirs Expert Systems Slide 5
The Nature of Expertise Necessary Expert Traits
• Be Recognized as an Expert• Know how they perform the task
• Have the time and ability to explain how they perform
• Can NOT just act intuitively without being able to explain their behaviors
• Be Motivated to Cooperate
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CIS4330: Professor Kirs Expert Systems Slide 6
The Nature of Expertise How do you know who is an expert??
• Also NOT an easy Question, although some are obvious
• There are references, However (a few off the Internet):• ExpertPages.com: A directory for legal professionals in search of
experts, expert witnesses, or consultants. Search by state, country, or subject area. http://www.expertpages.com/
• Experts Directory A searchable directory of experts from the legal, medical, journalism and other professions. http://www.experts.com
Are they really Experts ??? Don’t Mortgage the House!
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CIS4330: Professor Kirs Expert Systems Slide 7
Expert System Characteristics“An expert system is a computer program that represents and reasons with knowledge of some specialist subject with a view to solving problems or giving advice.” Jackson (1999)
Turing Test
1912-54
• A computer program demonstrates artificial intelligence if it can “pass’ as a human (c. 1950)
• In 1990, the Cambridge Center for Behavioral Studies began offering the $100,000 Loebner Prize to the first program whose responses were indistinguishable from a human’s
(No one has ever won)
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CIS4330: Professor Kirs Expert Systems Slide 8
Expert System Characteristics• Gary Kasparov vs. IBM’s Deep Blue
• May 11, 1997
• Garry Kasparov resigned 19 moves into Game 6
• Deep Blue wins the Best of Six game series 3.5 to 2.5
• IBM Development Team wins $700,000
• Kasparov wins $400,000
• The first win by a computer program over an International Grand Master since man/computer games were first began in 1970
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CIS4330: Professor Kirs Expert Systems Slide 9
Expert System Characteristics Basic Requirements
• simulates human reasoning
• Rule/Heuristic Based:
Rule: If there is a potato in the tailpipe, the car will not start.Finding: There is a potato in the tailpipe.Conclusion: The car will not start.
(Truth preserving inference)
Rule: If there is a potato in the tailpipe, the car will not start.Finding: My car will not start.Conclusion: Therefore, there is a potato in the tailpipe.
(Non-Truth preserving inference)
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CIS4330: Professor Kirs Expert Systems Slide 10
Expert System Characteristics Basic Requirements
• simulates human reasoning • Inference Engines
• Reasons with any rule constructed via rule set manager
• Searches for applicable rules
• Evaluates the predicates of those rules to determine their “truth”
• Executes the actions specified in “fired” (activated) rules
• The ‘Driving’ Force in an Expert System
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CIS4330: Professor Kirs Expert Systems Slide 11
Expert System Characteristics Basic Requirements
• simulates human reasoning • Inference Engines
• Corresponds to the idea of Deductive reasoning
TheoryTheoryTheoryTheory
HypothesisHypothesisHypothesisHypothesis
ObservationObservationObservationObservation
ConfirmationConfirmationConfirmationConfirmation
• Forward Chaining
RejectionRejectionRejectionRejection
Birds can Fly
Ostriches Can Fly
(I Fly to Australia)
OK – I was wrong !
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CIS4330: Professor Kirs Expert Systems Slide 12
Expert System Characteristics Basic Requirements
• simulates human reasoning • Inference Engines
• Consists of a condition part and an action part
• Conditions (rules) are matched against the database
• The forward chaining engine cycles repeatedly until it runs out of rules or a rule instructs it to stop.
• If true, the action is fired
• Corresponds to the idea of Deductive reasoning
• Forward Chaining
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CIS4330: Professor Kirs Expert Systems Slide 13
Expert System Characteristics Basic Requirements
• simulates human reasoning • Inference Engines
ObservationObservationObservationObservation
PatternPatternPatternPattern
Tentative HypothesisTentative HypothesisTentative HypothesisTentative Hypothesis
TheoryTheoryTheoryTheory
• Corresponds to the idea of Inductive reasoning
• Forward Chaining• Backward Chaining
I’m back in The Australian Outback – Bird watching
Birds Flying, but no Ostriches
Ostriches Can’t Fly (what a Moron I was!)
Not all Birds can Fly
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CIS4330: Professor Kirs Expert Systems Slide 14
Expert System Characteristics Basic Requirements
• simulates human reasoning
• Involves trying to prove a given goal by using rules to generate sub-goals and recursively trying to satisfy them.
• The engine looks at conclusions and determines all rules that could reach that conclusion
• Each rule is then examined for its premises
• If true, the rule is fired and a value is established
• The process continues until all possible solutions are generated
• Inference Engines
• Corresponds to the idea of Inductive reasoning
• Forward Chaining• Backward Chaining
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CIS4330: Professor Kirs Expert Systems Slide 15
Expert System Characteristics Basic Requirements
• simulates human reasoning • Knowledge Representation
• A repository (Database) of data and metadata
• Contains all the Rules established by the manager
• Knowledge Bases
• The data are stored as objects, which can be fired as needed
• Includes Symbolic data
• Includes Relationships between data
• May be used in conjunction with a standard database
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CIS4330: Professor Kirs Expert Systems Slide 16
Expert System Characteristics Basic Requirements
• simulates human reasoning • Knowledge Representation • Deal with realistically complex Problems • Reach Multiple Conclusions
• Especially as a result of backward chaining
• Explain the conclusions reached• The logic used must be demonstratable
• Deal with Missing Information• “Fuzzy Logic”• Non-numerical Analysis
• Demonstrate High Performance• Should approximate the performance of the
expert
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CIS4330: Professor Kirs Expert Systems Slide 17
Expert System Characteristics Basic Requirements ES Components
Inference Engine
User Interface
DatabaseKnowledge
Base
ES ShellA rule engine and
scripting Environment
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CIS4330: Professor Kirs Expert Systems Slide 18
Decision Support Systems Expert Systems
Expert System Characteristics Basic Requirements
Differences Between ES and DSS
• Based On Expert • No Experts Available• Based on Logical Reasoning • Based on Numerical Analysis• System Questions User • User Questions System• Used Frequently • Used for Ad-hoc Problems
• Final Solution(s) Provided • Outputs provided based Analysis • Very Accurate • Unknown Accuracy • Multiple Solutions • Always the same output • Learning Possible • Always the same output
ES Components
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CIS4330: Professor Kirs Expert Systems Slide 19
Additional Topics Knowledge Acquisition
“The transfer and transformation of potential problem-solving expertise from some knowledge source to a program” - Buchanan et al. (1983)
• Transfer of the Expert’s Knowledge as a set of rules into the Knowledge Base
• Since the Expert is not expected to code the rules, a Knowledge Engineer is required• lengthy & intense interviews Required• slow (2 to 5 units of knowledge /day)
??? Why ??? • Imprecise, illogical, jargon or colloquialisms, experience, contextual detail, reliability of sources, ...
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CIS4330: Professor Kirs Expert Systems Slide 20
Additional Topics Knowledge Acquisition
• Example: How to find a forgotten Password:
Expert (Computer Center Guru): Well, if it’s a YP pass-word, I first log on as root on the YP master
KE: (Knowledge Engineer): Er, what’s the YP master?
Expert: It’s the diskful machine that contains a database of network information
KE: ‘Diskful’ meaning - ?
Expert: -it has the OS installed on local disk
KE: Ah. (scribbles furiously) So you log on…
Expert: As root. Then I edit the password datafile, remove the encrypted entry, and make the new password map...
This is the weakest link in the process !!
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CIS4330: Professor Kirs Expert Systems Slide 21
Additional Topics Knowledge Acquisition
• Potential Solutions/Problems• automated knowledge elicitation
• interactive programs/automated conversation • Problem: There are no Good Programs available (yet)
• textual scanning
• Parsing of conversations to extract the important components
• Problem: NLP is still in its infancy
• machine learning • deriving decision rules from examples
• Problem: Only Limited Success to date
I don’t get it !
Me Neither• evaluating / weighting rules • performance optimization of rules
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CIS4330: Professor Kirs Expert Systems Slide 22
Additional Topics Knowledge Acquisition Knowledge Assessment
• logical adequacy • sound & complete inferencing
• heuristic Power• efficiency Vs. optimality (Effectiveness)
• notational Convenience• How accurately do the rules reflect
the logic?
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CIS4330: Professor Kirs Expert Systems Slide 23
Additional Topics Knowledge Acquisition Knowledge Assessment Explanation Facility
• Necessary to check validity of Solutions
• The Chain of reasoning must be logged
• Solution Accountability must be determined
• Deficiencies must be corrected
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CIS4330: Professor Kirs Expert Systems Slide 24
Additional Topics Knowledge Acquisition Knowledge Assessment Explanation Facility
• LISP (LISt Processor)
• Prolog
• CLIPS (Free Download: http://www.ghg.net/clips/CLIPS.html)• Jess (Free Download: http://herzberg.ca.sandia.gov/jess/ )
Available Packages/Tools
• Others: A good list can be found at
http://www-2.cs.cmu.edu/afs/cs/project/ai-repository/ai/areas/expert/systems/0.html
• Symbolic Manipulation Languages
• Expert Shells
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CIS4330: Professor Kirs Expert Systems Slide 25
????????????? Any Questions
(Please !!!) ?????????????
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CIS4330: Professor Kirs Expert Systems Slide 26