Other Approaches to Uncertain Reasoning

• Default Reasoning
  • statements assumed true in the absence of contradictory evidence

• Rule-based methods
  • Locality
    • if A=>B and A, then B without considering other evidence

  • Detachment
    • once B concluded, then used despite dependence on A

  • These previous two approaches allow more efficiency but are not appropriate for uncertain reasoning.

  • add certainty factors (MYCIN)
    • This can lead to incorrect inferences.

• Representing Ignorance
  • Dempster-Shafer theory

  • This computes a belief function.
    • This is the probability that the evidence supports the proposition.

    • This is not the probability of the proposition itself.

• Representing Vagueness
  • Fuzzy sets and fuzzy logic

  • Propositions are no longer true or false, but are assigned a truth value that is a number between 0 and 1.

  • This gives an evaluation of sentences that is similar to certainty factors.
    • Fuzzy logic

  • vagueness on meaning is not uncertainty