Knowledge Representation and Inference

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Knowledge Representationand Inference

• CS 480/580
• Fall 2009

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Requirements for Knowledge Representation
Languages

• Well-defined syntax and semantics
• General requirements
• Representational adequacy
• Inferential adequacy
• Inferential efficiency
• Clear syntax and semantics
• Naturalness

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Semantic Networks

• Originally developed in 1960s to represent the
  meaning of English words

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Frames

• Frames are a variant of semantic networks
• Widely used in expert systems
• Semantic networks and frames are interchangeable
• Defaults and multiple inheritance
• Slots and procedures

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Predicate Logic

• This is the most important knowledge
  representation
• Syntax
• P V Q
• P Q
• Q
• P ? Q
• P ? Q
• P (Q ? R) (Q V R) ? P

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Predicate Logic (cont.)

• Notation Begin with lower case letters for
  constants Begin with a capital letter for
  variables fatherof(allison, richard)
• Prolog uses , and OR
• More on Prolog

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Rule-based Systems

• If then rules and facts
• Forward chaining system
• Conflict resolution
• Backward chaining system