CPSC 415

Solutions to in-class predicate logic exercise

Here are the solutions to Thursday’s in-class predicate logic exercise:

  1. Can we prove ¬Teaching(Zeitz, 419)? Yes, with KB sentences 1, 26, 39, and 44. (Note that sentence 29 is not needed here!)
  2. Can we prove Overcommitted(Zeitz)? Nope. (Might or might not be actually true, but the current KB contents cannot prove it.)
  3. Can we prove ¬ChairOf(Stephen, CPSC)? Yes, with sentences 4, 18, 32, 36, and 41.
  4. Can we prove ChairOf(Farnsworth, CPSC)? Nope. (And in fact this is false.)
  5. Can we prove MemoryLoss(Ian)? This one is actually “it depends” on whether we’re using standard first-order logic semantics, or database semantics. (More on this in class Tuesday.) If the former, then no we cannot prove this, for the following reason: just because Ian is teaching 110 and 240 (from sentences 5 and 42), that doesn’t mean he’s necessarily not also teaching something else, which our KB doesn’t have a record of. If the latter, then we’re assuming “anything not asserted as true is considered false,” and so yes this sentence is provable, using KB sentences 5, 9, 14, 15, 23, 29, 42, and 43..

Stephen Davies