CS B552

Knowledge-Based Artificial Intelligence

Sample Problems for Midterm Exam

The midterm will be in class on Wed, March 29. Unless otherwise stated, you will be responsible for all material covered in class, readings and homework through Wednesday, March 22. The exam is closed book but you may bring an 8.5 x 11 inch sheet with notes on one side. Each student must prepare his or her own notes sheet.

These practice questions are aimed at giving a feeling for the types of questions on the midterm and helping you start your review of the material. They will not be handed in, but there will be a review/question session Saturday March 25, in IW107. The session will begin at 12:30pm and continue as long as there are questions. If you can’t make that session or have questions not covered there, please stop by any of our office hours and we’ll be glad to help!

Note that some of these questions are longer than would be on the midterm, to cover more ground as a review.

1. Explain the knowledge principle. Very briefly, what evidence supports it?

2. The AM system applies heuristics to transform mathematical concepts into other (hopefully more interesting) concepts. For example, it includes

If very few examples of a concept X are found, then add to the agenda the task of finding a generalization of X.

Suppose the basic approach of the AM system was being applied to finding interesting recipes instead of interesting mathematical concepts.

a) Describe the antecedent and consequent of a reasonable if-then heuristic to assess a recipe and (if the antecedents were satisfied) place on the agenda the task of finding a variant recipe. The heuristic should (1) be usable for a fairly broad class or recipes, (2) involve conditions which would be fairly easy to implement, using basic background knowledge on cooking (e.g., such as ingredient knowledge along the lines of that in CHEF), and (3) should yield a recipe likely to be more interesting.

b) Why would you expect the result to be more interesting than the original recipe?

3. Sometimes rule chaining in rule-based systems can lead to conflicting conclusions.

a) Briefly propose three ways a rule-based system could determine which conclusion to favor, after it has derived some conflicting conclusions (note that this question is not asking about conflict resolution methods for deciding which rule to apply, but asking you to come up with new methods for maintaining the system’s knowledge base). This might involve some modifications to the system.

1) First method:

2) Second method:

3) Third method:

b) Pick two of the three and state one advantage and one drawback of each (refer to them by their numbers in the above)

4. Conceptual dependency (CD) theory strictly limits the number of primitive actions allowed in CD representations. What are the tradeoffs involved in this restriction? Specifically,

a) State one advantage of restricting the vocabulary of primitives for CD. Illustrate by contrasting a CD primitive of your choice to a possible primitive from a bad knowledge representation you make up.

b) State one disadvantage restricting the vocabulary of primitives for CD. Illustrate with an example.

5. Conceptual dependency (CD) theory attempts to generate unambiguous representations. For the sentence “Sue took the test”, explain (in a few words each) two possible disjoint meanings and write a CD representation of each.

a) Meaning 1 (describe in English):

b) CD 1:

c) Meaning 2 (describe in English)

d) CD 2

6. Summarize the differences between scripts and MOPs and how they affect behavior of the systems that use them.

7 “When CBR systems learn, they generalize indices but not cases.” (This contrasts with learning methods which immediately generalize examples and then throw the examples away, retaining only the generalizations.)

a) What is the advantage of generalizing indices, rather than using only specifics of the situation as indices? Give an example.

b) What is an advantage of keeping cases in ungeneralized form (in addition to the low cost of storage)? Give an example