CS267 Fall 2011Practice Midterm

To study for the midterm I would suggest you: (1) Know how to do (by heart) all the practice problems. (2) Go over your notes at least three times. Second and third time try to see how much you can remember from the first time. (3) Go over the homework problems. (4) Try to create your own problems similar to the ones I have given and solve them. (5) Skim the relevant sections from the book. (6) If you want to study in groups, at this point you are ready to quiz each other. The practice midterm is below. Here are some facts about the actual midterm: (a) It is closed book, closed notes. Nothing will be permitted on your desk except your pen (pencil) and test. (b) You should bring photo ID. (c) There will be more than one version of the test. Each version will be of comparable difficulty. (d) One problem (less typos) on the actual test will be from the practice test.

1. Explain how the dictionary-as-a-string can be used to save space on the construction of the index dictionary.
2. What is a per-term index? How does it improve posting list look-up speed over binary search?
3. What is dictionary interleaving? What does the dictionary look like when dictionary interleaving is used?
4. With regard to hash-table chaining, what are the move-to-front and insert-at-back heuristics?
5. Give the formula for BM25. How can binary heaps be used to speed up document-at-a-time query processing?
6. What are some advantages of computing the disjunction of the query terms as opposed to the conjunction? What some advantages of computing the conjunction over the disjunction?
7. What is an accumulator in query processing? How does accumulator pruning work?
8. Express the Shakespeare corpus query: 'the speaker who said "Romeo, Romeo, wherefore art thou Romeo?"', using our region algebra.
9. What is the Source Coding Theorem?
10. What is a gamma code?