Next: 9. PROGRAMMING PROJECT #2. Up: SNePS: AN INTERACTIVE APPROACH Previous: 7.3. EXERCISE: Node-Based Inference

# 8. PROGRAMMING PROJECT #1.

(For the purposes of this exercise, noun phrases such as `circus elephant', `circus performer', `AI course instructor', `colorful costumes', etc., don't have to be broken down into their components.)

1. Start a new SNePS session. Represent the following information.

1. Elephants are animals.
2. A circus elephant (i.e., any/every circus elephant) is an elephant.
3. Dumbo is a circus elephant.
4. Clyde is an elephant
5. A trunk is an appendage.
6. Alex is an AI course instructor.
7. Tweety is a bird.

Show the following questions being answered correctly:

1. Is Dumbo an animal? (Should be "yes".)
2. Is Alex an animal? (Should be "no"/"I don't know".)

2. Represent the following information:

1. Elephants have trunks.
3. A head has a mouth.
4. Circus performers have colorful costumes.

Show the following questions being answered correctly:

1. Does Clyde have a mouth? (Should be "yes".)
2. Do elephants have appendages? (Should be "yes".)

3. Represent the following information:

1. Elephants are gray.
2. AI course instructors are insane.

Show the following questions being answered correctly:

1. Are circus elephants gray? (Should be "yes".)
2. Is Alex insane? (Should be "yes".)

4. Represent the following information:

1. Birds fly.
2. Dumbo can fly.
3. Elephants can play.

Show the following questions being answered correctly:

1. Can Tweety fly? (Should be "yes".)
2. Can elephants fly? (Should be "yes".)

Note: This exercise was adapted from Charniak & McDermott 1985. They consider "x can fly" if any x can fly.

Note that "Elephants can fly" is ambiguous (in ordinary English) between "All elephants can fly" and "some elephants can fly". The latter reading is true if Dumbo can fly. And, on that latter reading, it doesn't follow that Clyde can fly. However, since question 4b is, admittedly, odd, answer it as you see fit, clearly explaining any problems you see with it, as well as clarifying your answers.

Here's something else to consider: What if we give Cassie a rule saying that there exists exactly one elephant who can fly and then assert that Dumbo is that elephant? Then, when asked whether Clyde can fly, Cassie will surely say "no", right? Try it!

On the other hand, what happens if Dumbo has baby elephants who can also fly? The point is if there ever exists a second elephant that can fly, then saying there is exactly one elephant that can fly is not very useful. The fact that the only flying elephant that we know of happens to be Dumbo should not mean that he is the only flying elephant that exists or ever will exist.

3. Can Clyde fly? (Should be "no"/"I don't know".)
4. Can Clyde play? (Should be "yes".)

Next: 9. PROGRAMMING PROJECT #2. Up: SNePS: AN INTERACTIVE APPROACH Previous: 7.3. EXERCISE: Node-Based Inference
William J. Rapaport 2003-09-22