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Avoiding Errors in Representing Knowledge

Learn to avoid common errors in representing knowledge, such as using vague constant names, relying on NL, and problems with variables. Understand the importance of meaningful variable names and proper variable typing.

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Avoiding Errors in Representing Knowledge

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  1. Errors in Representing Knowledge • Errors with Constants, Variables, and Reliance on NL • Errors with Specialization, Generalization, and Rules • Other Errors

  2. Letting NL dictate your representation For Example: has • John “has” a headache • John “has” pride • John “has” a son • John “has” $50 (“has”#$John #$Headache) (“has”#$John #$Pride) (“has” #$John #$JohnsSon) (“has”#$John (#$Dollar-US 50))

  3. At least 4 different senses: (#$bodilyDoer #$John #$JohnsHeadache) (#$feelsEmotion #$John #$Pride) (#$children #$John #$JohnsSon) (#$ownsWealth #$John (#$Dollar-US 50)) • John “has” a headache • John “has” pride • John “has” a son • John “has” $50

  4. Relying on Constant Names • #$Coral - color, substance, or life form? • #$Turkey - nation, or bird? • Unless you’ve examined the assertions on the term, you don’t really know what it stands for.

  5. Using Vague Constant Names • #$Coral- color, ocean floor feature, or life form? • #$Turkey- nation, or bird? When possible, disambiguate: • #$Coral-Color, #$CoralReef, #$CoralPolyp • #$Turkey, #$Turkey-Bird

  6. Problems with Variables:Meaningless Variable Names Bad:?X, ?Y, ?Z, ?X1, ?X2, ?XX, ?XXX, etc. Good:?SUPER, ?SUB, ?EVNT, ?AGNT, etc. Readability is important! Where’s the error? (#$implies (#$and (#$startsAfterEndingOf ?X ?Y) (#$temporallySubsumes ?X ?Z)) (#$startsAfterEndingOf ?Y ?Z))

  7. Problems with Variables:Meaningless Variable Names It’s easier to spot here, isn’t it? (#$implies (#$and (#$startsAfterEndingOf ?LATE ?EARLY) (#$temporallySubsumes ?LATE ?LATE-SUB)) (#$startsAfterEndingOf ?EARLY ?LATE-SUB))

  8. Problems with Variables:Check them carefully! Typos are hard to spot and can have unintended effects! (#$implies (#$and (#$isa ?CIRC #$Circle) (#$radius ?CIRC ?RAD)) (#$evaluate ?AREA (#$TimesFn #$Pi-Number ?RAD ?RAD))) (#$areaOfObject ?CIRCLE ?AREA))

  9. Problems with Variables:Typing. Variables aren’t typed by their names: (#$implies (#$and (#$inCont-Open ?RIVER ?CANYON) (#$inCont-Open ?BOAT ?CANYON)) (#$in-Floating ?BOAT ?RIVER)) These must be added: (#$isa ?RIVER #$River) (#$isa ?CANYON #$Canyon) (#$isa ?BOAT #$Watercraft)

  10. Problems with Variables:Typing. Types implied by arg constraints on relations should NOT be added, as this redundancy violates modularity: (#$implies (#$and (#$isa ?PERS #$Person) (#$coworkers ?PERS ?CO)) (#$acquaintedWith ?PERS ?CO)) Instead: (#$implies (#$coworkers ?PERS ?CO) (#$acquaintedWith ?PERS ?CO))

  11. Summary • Letting NL dictate your representation • Relying on Constant Names • Using Vague Constant Names • Problems with Variables • Meaningless variable names • Typos in naming variables • Variable Typing

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