Slide trí tuệ nhân tạo chapter6 1 knowledge representation
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Knowledge Representation
Chapter 6
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What is KR?
R. Davis, H. Schrobe, P. Szolovits (1993): “What is a
knowledge representation?”
Cao Hoang Tru
CSE Faculty - HCMUT
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03 April 2010
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What is KR?
R. Davis, H. Schrobe, P. Szolovits (1993):
1. A surrogate
2. A set of ontological commitments
3. A fragmentary theory of intelligent reasoning
4. A medium for efficient computation
5. A medium of human expressions
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CSE Faculty - HCMUT
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Representation and Mapping
• Facts: things we want to represent.
• Representations of facts: things we can manipulate.
Cao Hoang Tru
CSE Faculty - HCMUT
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Representation and Mapping
reasoning
programs
Facts
Internal
Representations
English
understanding
English
generation
English
Representations
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CSE Faculty - HCMUT
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Representation and Mapping
Initial
facts
desired real reasoning
forward
representation
mapping
Internal
representations
of initial facts
Cao Hoang Tru
CSE Faculty - HCMUT
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Final
facts
backward
representation
mapping
operation
of program
Internal
representations
of final facts
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Representation and Mapping
• Spot is a dog
• Every dog has a tail
Spot has a tail
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CSE Faculty - HCMUT
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Representation and Mapping
• Spot is a dog
dog(Spot)
• Every dog has a tail
"x: dog(x) hastail(x)
hastail(Spot)
Spot has a tail
Cao Hoang Tru
CSE Faculty - HCMUT
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Representation and Mapping
• Fact-representation mapping is not one-to-one.
• Good representation can make a reasoning program
trivial.
Cao Hoang Tru
CSE Faculty - HCMUT
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03 April 2010
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Representation and Mapping
The Multilated Checkerboard Problem
“Consider a normal checker board from which two
squares, in opposite corners, have been removed.
The task is to cover all the remaining squares exactly
with donimoes, each of which covers two squares. No
overlapping, either of dominoes on top of each other or
of dominoes over the boundary of the multilated board
are allowed.
Can this task be done?”
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CSE Faculty - HCMUT
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Representation and Mapping
No. black squares
= 30
No. white square
= 32
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CSE Faculty - HCMUT
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Representation and Mapping
Good representation:
• Representational adequacy
• Inferential adequacy
• Inferential efficiency
• Acquisitional efficiency
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CSE Faculty - HCMUT
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Approaches to KR
Simple relational knowledge:
• Provides very weak inferential capabilities.
• May serve as the input to powerful inference engines.
Cao Hoang Tru
CSE Faculty - HCMUT
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03 April 2010
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Approaches to KR
Inheritable knowledge:
• Objects are organized into classes and classes are
organized in a generalization hierarchy.
• Inheritance is a powerful form of inference, but not
adequate.
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CSE Faculty - HCMUT
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Approaches to KR
Inferential knowledge:
• Facts represented in a logical form, which facilitates
reasoning.
• An inference engine is required.
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CSE Faculty - HCMUT
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Approaches to KR
Procedural knowledge:
• Representation of “how to make it” rather than “what
it is”.
• May have inferential efficiency, but no inferential
adequacy and acquisitional efficiency.
Cao Hoang Tru
CSE Faculty - HCMUT
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03 April 2010
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Approaches to KR
Choosing the Granularity:
• High-level facts may not be adequate for inference.
• Low-level primitives may require a lot of storage.
Cao Hoang Tru
CSE Faculty - HCMUT
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Homework
Reading
R. Davis, H. Schrobe, P. Szolovits (1993): “What is a knowledge
representation?”
Cao Hoang Tru
CSE Faculty - HCMUT
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18
03 April 2010
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