Exercise 1.19

In the permuterm index, each permuterm vocabulary term points to the original vocabulary term(s) from which it was derived. How many original vocabulary terms can there be in the postings list of a permuterm vocabulary term?

My Answer:

如果是 original vocabulary 的话应该就是一个。(例如 hello$)

Exercise 1.20

Write down the entries in the permuterm index dictionary that are generated by the term mama.

My Answer:

mama$ , ama$m , ma$ma , a$mam , $mama

Exercise 1.21

If you wanted to search for s*ng in a permuterm wildcard index, what key(s) would one do the lookup on?

My Answer:

根据书中的方法，得到 ng$s*。

Exercise 1.22

Refer to Figure 3.4 ; it is pointed out in the caption that the vocabulary terms in the postings are lexicographically ordered. Why is this ordering useful?

Exercise 1.23

Consider again the query fimoer from Section 3.2.1 . What Boolean query on a bigram index would be generated for this query? Can you think of a term that matches the permuterm query in Section 3.2.1 , but does not satisfy this Boolean query?

My Answer:

The Boolean query is f AND fi AND mo AND er AND r, filibuster 这不满足 boolean query，但是满足 permuterm query。

Exercise 1.24

Give an example of a sentence that falsely matches the wildcard query mon*h if the search were to simply use a conjunction of bigrams.

My Answer:

Monday hash。