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Next: 7. NODE-BASED INFERENCE (UM Ch. 3). Up: 6. PATH-BASED INFERENCE (UM§2.5.2). Previous: 6.7. Finding Asserted Information

6.8. EXERCISES: Defining Paths

  1. Extend the relation has so that it "distributes" over isa. I.e., define has so that X has Y if X isa A and A has B and B isa Y. In general, we want this:
    has <= isa* has+ isa*
    I.e., the has path is defined as 0 or more isa relations, followed by 1 or more has relations, followed by 0 or more isa relations. (This is tricky. You'll need to remember to use asserted nodes in your path, and you'll want to start out at an asserted node!)
  2. What has a mouth?
  3. What does Dumbo have?
  4. For more practice with paths, see what response you get when you try these:
    (find (object- isa) animal)
    (find (object- isa object- isa) animal)
    (find (object- isa object- isa object- isa) animal)

William J. Rapaport 2003-09-22