Chapter5 Knowledge Reasoning and Inferencing

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Chapter5 Knowledge Reasoning and Inferencing

• ????? 5 ????????????????????????
• Sasalak Tongkaw

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???????????????

• Durkin (1994) ???????? ???????????????
  ???????????????????????????? ????????
  ??????????????????????????????????????????

• Deductive
• Inductive
• Abductive

• Analogical
• Common-Sense

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1.Deductive Reasoning

• Rule I an standing in the raingtI will get wet
• Axiom I am standing in the rain
• Conclusion I will get wet

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2.Inductive Reasoning

• Axiom1 Monkeys in the National Zoo eat bananas
• Axiom2 Monkeys in the Songkhla Zoo eat bananas
• Conclusion All monkeys eat bananas

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3.Abductive Reasoning

• Rule It is raininggt ground is wet
• Axiom ground is wet
• Conclusion Is it raining?

No may be it wet because of pouring water
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4.Analogical Reasoning

• Tiger has four legs, Eats meat
• Lives in India and Southeast Asia
• Lion look like tiger
• Conclusion Lion has four legs,Eats meat
• Lives in India and Southeast Asia

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5.Common-Sense Reasoning

• ?????????? ???????????????????????????????????????
  ??????????????????? ??????????? common-sense ????
  ??????????????????????????????????????????????????
  ???????????

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Inference techniques

• Modus Ponens
• Hypothethical syllogism
• Modus Tollens
• Resolution

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Modus Ponens

• If X then Y
• X is True
• Conclusion Y is True

X gt Y X Conclusion Y
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Hypothethical Syllogism

• If X then Y
• If Y then Z
• Conclusion If X then Z

X gt Y Y gt Z Conclusion XgtZ
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Modus Tollens

• If A then B
• not B
• Conclusion not A

A gt B B Conclusion A
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Forward Chaining

• given a set of basic facts, we try to derive a
  conclusion from these facts
• example What can we conjecture about Clyde?

IF elephant(x) THEN mammal(x) IF mammal(x) THEN
animal(x) elephant (Clyde)
unification find compatible values for
variables
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Forward Chaining Example
IF elephant(x) THEN mammal(x) IF mammal(x) THEN
animal(x) elephant(Clyde)
unification find compatible values for variables
IF elephant( x ) THEN mammal( x )
elephant (Clyde)
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Forward Chaining Example
IF elephant(x) THEN mammal(x) IF mammal(x) THEN
animal(x) elephant(Clyde)
unification find compatible values for variables
IF elephant(Clyde) THEN mammal(Clyde)
elephant (Clyde)
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Forward Chaining Example
IF elephant(x) THEN mammal(x) IF mammal(x) THEN
animal(x) elephant(Clyde)
unification find compatible values for variables
IF mammal( x ) THEN animal( x )
IF elephant(Clyde) THEN mammal(Clyde)
elephant (Clyde)
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Forward Chaining Example
IF elephant(x) THEN mammal(x) IF mammal(x) THEN
animal(x) elephant(Clyde)
unification find compatible values for variables
IF mammal(Clyde) THEN animal(Clyde)
IF elephant(Clyde) THEN mammal(Clyde)
elephant (Clyde)
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Forward Chaining Example
IF elephant(x) THEN mammal(x) IF mammal(x) THEN
animal(x) elephant(Clyde)
unification find compatible values for variables
animal( x )
IF mammal(Clyde) THEN animal(Clyde)
IF elephant(Clyde) THEN mammal(Clyde)
elephant (Clyde)
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Forward Chaining Example
IF elephant(x) THEN mammal(x) IF mammal(x) THEN
animal(x) elephant(Clyde)
unification find compatible values for variables
animal(Clyde)
IF mammal(Clyde) THEN animal(Clyde)
IF elephant(Clyde) THEN mammal(Clyde)
elephant (Clyde)
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Backward Chaining

• try to find supportive evidence (i.e. facts) for
  a hypothesis
• example Is there evidence that Clyde is an
  animal?

IF elephant(x) THEN mammal(x) IF mammal(x) THEN
animal(x) elephant (Clyde)
unification find compatible values for
variables
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Backward Chaining Example
IF elephant(x) THEN mammal(x) IF mammal(x) THEN
animal(x) elephant(Clyde)
unification find compatible values for variables
animal(Clyde)
IF mammal( x ) THEN animal( x )
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Backward Chaining Example
IF elephant(x) THEN mammal(x) IF mammal(x) THEN
animal(x) elephant(Clyde)
unification find compatible values for variables
animal(Clyde)
IF mammal(Clyde) THEN animal(Clyde)
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Backward Chaining Example
IF elephant(x) THEN mammal(x) IF mammal(x) THEN
animal(x) elephant(Clyde)
unification find compatible values for variables
animal(Clyde)
IF mammal(Clyde) THEN animal(Clyde)
IF elephant( x ) THEN mammal( x )
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Backward Chaining Example
IF elephant(x) THEN mammal(x) IF mammal(x) THEN
animal(x) elephant(Clyde)
unification find compatible values for variables
animal(Clyde)
IF mammal(Clyde) THEN animal(Clyde)
IF elephant(Clyde) THEN mammal(Clyde)
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Backward Chaining Example
IF elephant(x) THEN mammal(x) IF mammal(x) THEN
animal(x) elephant(Clyde)
unification find compatible values for variables
animal(Clyde)
IF mammal(Clyde) THEN animal(Clyde)
IF elephant(Clyde) THEN mammal(Clyde)
elephant ( x )
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Backward Chaining Example
IF elephant(x) THEN mammal(x) IF mammal(x) THEN
animal(x) elephant(Clyde)
unification find compatible values for variables
animal(Clyde)
IF mammal(Clyde) THEN animal(Clyde)
IF elephant(Clyde) THEN mammal(Clyde)
elephant (Clyde)
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Forward vs. Backward Chaining
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The End of Chapter 5