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)