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Spring 2006 Artificial Intelligence COSC40503 week 9


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Title: Spring 2006 Artificial Intelligence COSC40503 week 9

Spring 2006 Artificial Intelligence
COSC 40503 week 9
  • Antonio Sanchez
  • Texas Christian University

The IF THEN contingency model
In the early 1970 Ed Feigenbaum at Stanford
began working with a simple model to codify
knowledge, a model so simple that people were
initially skeptical about the results however
they were so successful that the first true AI
application in industry took place. Expert
Systems made AI known outside of the academic
field. Basically the idea behind the model is
to represent the relation between two pieces of
data as an Implication IF Antecedent
THEN Consequent A gt C (here the concept of
implication is the Key)
The IF THEN equivalents
IF Antecedent THEN Consequent A gt C
Expert System Knowledge Base Inference Engine
  • A computer program that can advise, analyze,
    categorize, communicate, consult, design,
    diagnose, explain, explore, forecast, form
    concepts, identify, interpret, justify, learn,
    manage, monitor, plan, present, retrieve,
    schedule, test, and tutor. They address problems
    normally thought to require human specialists for
    their solution. (Michaelson, Michie, Boulanger

Expert Systems Components
  • User interface
  • Knowledge acquisition module Knowledge base
  • Inference engine
  • control strategy
  • Explanation facility
  • Diverse Interfaces

Expert System Architecture
Queries A good I/O interface with the user
Data Base General data (facts) is stored here
Results Diagnosis,synthesis Why? How?
Inference Search KD and DB to solve a
problem backward and forward tracking
Interface Syntactical and semantical processing
Knowledge Aquisition New rules IF/THEN
Administration Login users and journaling,
Knowledge Base IF THEN rules are stored here
Conditions Initial data conditions (facts)
  • There are basically four different processes when
    running an Expert System
  • Data Base Updating
  • Knowledge Acquisition
  • Queries
  • Why and How Questioning

Data Base Updating
Data Base
  • The DB is updated with the
  • data of facts and conditions for
  • a given situation

Data, conditions facts
Knowledge Acquisition
  • From Buchanan et al. (1983)
  • the transfer and transformation of potential
    problem solving expertise from some knowledge
    source to a program

  • The KB is enhanced with new rules
  • based on the expertise of various
  • the Experts in the field
  • Rules are organized in certain fashion

Knowledge Acquisition
New IF/THEN Rues
Knowledge Base
Backward chaining (DIAGNOSIS)
  • Begins with a proposed conclusion
  • Tries to match it with the then clauses of
  • Then looks at the corresponding if clauses
  • Tries to match those with assertions, or with the
    then clauses of other rules

Forward chaining SYNTHESIS
  • Begins with assertions and tries to match those
    assertions to if clauses of rules, thereby
    generating new assertions

Data Base
  • In generates an hypothesis
  • Tries to prove it either
  • Backwards (diagnosis)
  • Forwards (synthesis)

Knowledge Base
Why and How questions
Why? How?
Data Base
  • To answer WHY
  • It presents the proposed
  • tree traversal (forward)
  • To answer HOW
  • It presents the performed tree
  • traversal so far executed (backward)

Knowledge Base
Trend Setters
  • R1/XCON

Trend Setters
  • DENDRAL (Feigenbaum, Buchanan, Letterberg)
  • First expert system Analyzed NMR mass
    spectrogram data to determine the geometric
    arrangement of atoms in a molecule.
  • It is in routine use by chemists, and has
    contributed to refereed journal publications.

Trend Setters
  • MYCIN (Ted Shortliffe)
  • Knew about blood infections?
  • In one study, its recommendations were judged
    preferrable or equal to those of five experts.
  • INTERNIST (Harry Pople)
  • Broader medical expertise
  • In one study, it got 25 out of 43 diagnoses
    correct, compared to 28 for clinical physicians
    and 35 for experts.

Trend Setters
  • MYCIN (Ted Shortliffe)
  • Knew about blood infections
  • In one study, its recommendations were judged
    preferable or equal to those of five experts.
  • Sample Rule
  • IF
  • (1) the stain of the organism is gram-positive,
  • AND (2) the morphology of the organism is coccus,
  • AND (3) the growth confirmation of the organism
    is clumps,
  • THEN
  • there is suggestive evidence (0.7) that the
    identity of the organism is staphylococcus.

Trend Setters
  • PROSPECTOR (Hart and Duda)
  • It analyzed information from geological
  • It accurately identified the location and extent
    of ore grade mineralization for a previously
    unknown molybdenum deposit.
  • R1 (XCON) (John McDermott)
  • It was routinely used to configure every VAX sold
    by DEC.
  • Over 99 of the configurations were reported to
    be accurate, and most of the rest usable with
    minor corrections.
  • Most errors were reportedly due to lack of
    product information on recent products.
  • Famous because it was early large system
    --somewhere around 6,000 to 10,000 rules.

From 1990 On
  • There were over 5,000 expert systems in existence
  • 2 billion a year business

Classification and Applications
Source Peter R. Gillett, Rutgers University
  • Management
  • Advice on management by objectives
  • Selection and use of forecasting techniques
  • Analysis of failing companies
  • Scheduling of business trips and meetings
  • Human resources
  • Matching personnel to jobs
  • Arranging compensation packages
  • Diagnosis
  • hypothesizing a cause of a problem given some
    data points
  • Debugging and Repair
  • analyzing malfunctions and making recommendations
  • Interpretation
  • form high-level conclusions from collections of
    raw data.
  • Monitoring
  • comparing a system's observed behavior to its
    expected behavior
  • Control
  • governing the behavior of a complex environment
  • Design
  • finding configurations that meet some performance
    criteria or constraints
  • Planning
  • Instruction
  • detecting and correcting deficiencies in students
    understanding of a subject.
  • Finance and banking
  • Stock portfolio management
  • Asset-liability management
  • Loan approvals and auditing
  • Production
  • Fault diagnosis in networks and equipment
  • Complex bidding in the construction industry
  • Accounting and auditing
  • Estate planning and tax advice
  • Executing and analyzing internal auditing
  • Charging back costs in computer time-sharing
  • Auditing advanced EDP systems
  • Audit program development
  • Internal control evaluation
  • Risk analysis
  • Tax accrual and deferral
  • Disclosure compliance
  • Computers and Information Systems
  • Data center evaluation
  • Selection and maintenance of HS
  • Software development
  • Software selection
  • Information transfer

Expert System Details
  • Knowledge Acquisition
  • Knowledge Representation
  • Inference Resolution
  • Uncertainty
  • Limitations
  • Ontologies

Knowledge Engineering
  • Knowledge acquisition
  • Knowledge elicitation
  • Knowledge representation
  • Production rules
  • Semantic networks
  • Frames

Production Rules
  • Dominant paradigm for applications
  • Especially where textbook knowledge or heuristics
    are applied, can appear a very natural
  • Can pose problems when the number of rules grows
    excessively large
  • A method for resolving rule conflicts is needed

Example of Rules
  • PINEL Palacios, Sanchez (1985)
  • Psychological Disorders DIAGNOSTICS
  • Rule 1
  • Category Schizophrenia
  • IF There is incoherence ( 1/3, 1 ) AND
  • Absence of systematic delirium ( 1/3, 1 ) AND
  • Inappropriate affect ( 1/3, 1 )
  • THEN Disorganized Schizophrenia
  • Rule 6
  • Category Schizophrenia
  • IF Lack of hygienic appearance ( 1/3, 1 ) AND
  • Difficulties at job ( 1/3, 1 ) AND
  • Difficulties in establishing a relationship (
    1/3, 1 )
  • THEN Schizophrenia Criteria B
  • SEA Vazquez, Flammand, Sanchez, 1984
  • Agricultural expert System SYNTHESIS
  • Rule 14
  • IF of clay Xr AND of limus Xl
  • AND of sand lt Xs
  • THEN texture Xt
  • Rule 30
  • IF PHKCl gt 4 AND PHKCl lt 5
  • THEN quantity
  • 306.86-59.4PHKClclay in Kg/Ha of CaO

Example of Rules
Sistema ZYANYA Rodriguez,Sanchez (1992) EDP
Auditing SYNTHESIS R000 IF The computer is
located in a physically safe place AND The
entrance has a secure access control AND Only
authorized personnel with access codes are
allowed to use the system THEN The physical
security of the computer is probably
adequate R033 IF ( Feasibility analysis was
performed ) AND ( There is a quantifiable
product) AND ( NOT there is a control element
of the C,M,S type ) C058 THEN ( It is observed
that the execution of the study has contradicted
the nature of the C,M,S element ) R058 IF ( At
least the programming phase was executed ) C058
THEN ( Proceed to evaluate the coherence of the
methodology applied in the organization ) N001
ACTIVATE NODE ( Coherence of DLC methodology )
  • SEBT Gracian (1985)
  • Conveyor Design SYNTHESIS
  • Rule 3
  • Category Layers
  • IF 14 lt Width lt 20 AND Angle 20
  • THEN Consider 4 layers
  • Rule 50
  • Category Diameters
  • IF 14 lt Width lt 20 AND FPM lt 300
  • THEN Diameter 4

Example of Rules
WWTPS Cabezut, Sanchez (1995) Waste Water
Treatment Plants DIAGNOSTICS IF (disposer
and channel between Lagoon 4 Zahuapán River
is dirty) THEN inadequate flow of between
lagoon 4 and Zahuapán IF ( Lagoon 4 is calcium
filled AND disposer of Lagoon 4 is clean)
THEN shoulder strap water lt 2.60 m, AND
adequate load for Lagoon 4 IF (L4EA AND L4AA AND
elimination of the biochemical Oxygen demand in
Lagoon 4 AND L4RADBO (1-
(DBO3-DBO4)/DBO0)100 gt 10
Semantic Networks
  • Preceded frames, but are now less used. Seminal
    work by W. Ross Quillian
  • Represents knowledge relations as a network of
  • Useful when knowledge less hierarchical
  • Emphasize relationships rather than nodes

Inference Engines
  • Control Strategies
  • Forward chaining
  • Backward chaining
  • Search strategies
  • Depth first
  • Breadth first
  • Conflict resolution
  • RETE algorithm

Rule exploring Node Levels

LHS Antecedents Premises
RHS Consequents Conclusions
The ATM Example Information Knowledge
What is the rationality in rule 67, 81 or 95?
How about adding more rules like 69, 83, 97,
However there are more knowledge, consider for
example How much money? How much security? In
what order, are the rules sorted?
Search Strategies in the KB
  • By Knowledge area
  • By Node Level
  • By Synonym
  • By Complexity
  • By Number of Antecedents
  • By Use

LJournal Reference
RETE Algorithm in the KB By Use
Asumme you have a rule as follows IF a late
book exists, with name X, borrowed by someone
named Y AND that borrower's address is known
to be Z THEN send a late notice to Y at Z
about the book X.
(defrule library-rule-1 (book (name ?X)
(status late) (borrower ?Y)) (borrower (name
?Y) (address ?Z)) gt (send-late-notice
?X ?Y ?Z))
Only new facts are tested against any rule LHSs.
Additionally, new facts are tested against only
the rule LHSs to which they are most likely to be
relevant. As a result, the computational
complexity per iteration drops to something more
or less linear to the size of working memory.
Source http//herzberg.ca.sandia.gov/jess/docs/70
/rete.htm Rete A Fast Algorithm for the Many
Pattern/ Many Object Pattern Match Problem",
Charles L. Forgy, Artificial Intelligence 19
Inference under Uncertainty
  • Unreliable sources of information
  • Abundance of irrelevant data
  • Imprecision of language and perception
  • Lack of understanding
  • Hidden or unknown variables
  • Data difficult or expensive to obtain

Reasoning and Uncertainty
  • Sources of Uncertainty and Inexactness in
  • Incorrect and Incomplete Knowledge
  • Ambiguities
  • Belief and Disbelief
  • Probability Theory
  • Bayesian Networks
  • Dempster-Shafer Theory
  • Certainty Factors
  • Approximate Reasoning
  • Fuzzy Logic

Bayesian Approaches
  • Use a Bayesian Network by deriving the
    probability of a cause given a symptom
  • Specially useful in diagnostic systems
  • medicine, computer help systems
  • inverse or a posteriori probability
  • inverse to conditional probability of an earlier
    event given that a later one occurred

Advantages and Problems of Bayesian Reasoning
  • Advantages
  • sound theoretical foundation
  • well-defined semantics for decision making
  • Problems
  • requires large amounts of probability data
  • sufficient sample sizes
  • subjective evidence may not be reliable
  • independence of evidences assumption often not
  • relationship between hypothesis and evidence is
    reduced to a number
  • explanations for the user difficult
  • high computational overhead

Dempster-Shafer Theory
  • Mathematical theory of evidence
  • notations
  • frame of discernment FD
  • power set of the set of possible conclusions
  • mass probability function m
  • assigns a value from 0,1 to every item in the
    frame of discernment
  • mass probability m(A)
  • portion of the total mass probability that is
    assigned to an element A of FD

Belief and Certainty
  • Belief Bel(A) in a subset A
  • sum of the mass probabilities of all the proper
    subsets of A
  • likelihood that one of its members is the
  • Plausibility Pl(A)
  • maximum belief of A
  • Certainty Cer(A)
  • interval Bel(A), Pl(A)
  • expresses the range of belief

Source Dr. Franz J. Kurfess www.csc.calpoly.edu/
fkurfess/ Courses/480/F03/Slides/
Advantages and Problems of Dempster-Shafer
  • Advantages
  • clear, rigorous foundation
  • ability oto express confidence through intervals
  • certainty about certainty
  • Problems
  • non-intuitive determination of mass probability
  • very high computational overhead
  • may produce counterintuitive results due to
  • usability somewhat unclear

Source Dr. Franz J. Kurfess www.csc.calpoly.edu/
fkurfess/ Courses/480/F03/Slides/
Certainty Factors
  • Shares some foundations with Dempster-Shafer
    theory, but more practical
  • Denotes the belief in a hypothesis H given that
    some pieces of evidence are observed
  • No statements about the belief is no evidence is
  • in contrast to Bayes method

Source Dr. Franz J. Kurfess www.csc.calpoly.edu/
fkurfess/ Courses/480/F03/Slides/
Belief and Disbelief
  • measure of belief
  • degree to which hypothesis H is supported by
    evidence E
  • MB(H,E) 1 IF P(H) 1 (P(HE) -
    P(H)) / (1- P(H)) otherwise
  • measure of disbelief
  • degree to which doubt in hypothesis H is
    supported by evidence E
  • MB(H,E) 1 IF P(H) 0 (P(H) -
    P(HE)) / P(H)) otherwise

Certainty Factor
  • Certainty factor CF
  • ranges between -1 (denial of the hypothesis H)
    and 1 (confirmation of H)
  • CF (MB - MD) / (1 - min (MD, MB)
  • Example in Pinel
  • IF There is incoherence ( MD 1/3, MB 1 )
  • Absence of systematic delirium ( MD 1/3, MB
    1 ) AND
  • Inappropriate affect ( MD 1/3, MB 1 )
  • THEN ( IF Min(MB) - Max(MD) gt Threshold
  • gt
    Disorganized Schizophrenia )

Certainty Factor
Source http//www.expertise2go.com/webesie/tutori
  • Difficulties in identifying suitable human
    experts for development
  • Difficulties in eliciting expertise from humans,
    who may have problems in articulating their
  • Disagreements among experts
  • Consultations time-consuming relative to
    perceived value

When to use ES
  • // First Rule
  • For SYNTHESIS When there IS NOT a Function
    y f(x) or analytic model that represents
    it in the problem does not exists
  • OR
  • For DIAGNOSIS When there IS NOT an
    inverse Function x f(y) or analytic model
    that represents it in the problem does not exists
  • AND The task be clearly definable
  • AND A methodology has been delineated and
    knowledge may be elicited and can be structured
  • AND There is interdisciplinary group of experts
    in the area
  • AND When the task be not trivial

Then you use Expert Systems
When to use uncertainty
  • // Second Rule
  • The context universe of the application is
  • OR
  • There is little knowledge
  • OR There is lack of data
  • AND it is not easily obtainable
  • OR the data available is statistical in nature
  • OR the context universe of the application
    appears UNKNOWN due to the lack of IF/THEN rules

Then you use Uncertainty
Expert System Tools
  • Support prototyping
  • Shells
  • High-level programming languages
  • Multiple-paradigm programming environments (e.g.,
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