ES Program Structure

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ES Program Structure

• Action Block
• Rules Block
• Questions Block

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Action Block

• ACTION
• action statements

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action statements

• Display
• Find
• Get
• Put
• Menu
• Assignment
• Comment

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action statements

• DISPLAY text string or
• string1 variablename string2
• DISPLAY "Your credit request of CredRequest is
  Approval."

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action statements

• FIND variablename
• 1. Engine goes to first (next) Rule that
  contains variablename in its THEN clause. If
  there is none, it goes to the Questions.
• 2. Engine determines if the IF clause of the
  Rule is TRUE.
• 3. If TRUE, Engine returns the value assigned in
  the THEN clause.
• 4. If FALSE it returns to Step 1, and continues
  until there is a True in Step 3.

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Rules are sets of IF Statements

• IF logicexpression THEN variablename value
• See Page 42 of text

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action statements

• GET variablename fieldname, filename, ALL
• PUT filename
• MENU ...
• See Page 65 of text

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Assignment Statement

• variablename value
• 1. value is considered a string literal
• e.g. Member_status OK
• 2. If value is a variable, then the contents of
  the variable are assigned by
• variablename (value)
• e.g. NPA (NetPersonalAssets)
• 3. All variables have the initial value UNKNOWN

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Comment

• ! commentline
• Example
• ! This is the Income computation

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ES Program Structure

• Action Block
• Rules Block
• Questions Block

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Rules Block

• RULE label-1
• ifstatement
• ifstatement
• RULE label-2
• ifstatement
• See Page 30 of text

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ifstatement

• IF logicexpression THEN statements
• logicexpression
• 1. OR is stronger than AND
• a and b or c a and (b or c)
• 2. X operator Y (e.g. X gt Y)
• (1) If X is UNKNOWN, engine will
  automatically do a FIND
• (2) If Y is UNKNOWN it will not. You
  must first do a FIND Y

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ifstatement

• IF logicexpression THEN statements
• logicexpression
• 3. X operator Y
• If Y is an arithmetic expression, always
  write (Y).
• Example Income gt (3 Expense)

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ES Program Structure

• Action Block
• Rules Block
• Questions Block

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Questions Block

• ASK vblname promptstring
• ASK vblname promptstringCHOICES vblname
  value1, value2,
• ASK vblname promptstring
• MENU vblname, See Page 65

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The ProblemCredit Analysis by an Expert System

• Approval of a Credit Request for a given amount
• Customer has a credit record in a commercial
  credit database (CDB)
• Customer submits a file of information of current
  business data for his account (ADB)
• The government maintains an industry stability
  rating database (SRDB)
• Customer is asked questions during the session
  (UQ)