17 Questions
What is the main difference between postings lists in a nonpositional index and a positional index?
The presence or absence of a list of positions
What type of search does a positional index support?
Phrase search and proximity search
What is an example of a query that requires a proximity search?
employment /4 place
What is the purpose of a positional index?
To support phrase and proximity searches
What is an example of a document that would match the query 'employment /4 place'?
Employment agencies that place healthcare workers are seeing growth.
What is the simplest algorithm for proximity search using positional index?
Looking at the cross-product of positions of words in a document
What is a limitation of using positional indexes for proximity search?
They can be very inefficient for frequent words, especially stop words
What is the advantage of combining biword indexes with positional indexes?
It results in faster queries for frequent biwords
What is the benefit of using Next Word Index over positional indexes?
It is faster than positional indexes, but at a cost of more space
What is the purpose of including frequent biwords as vocabulary terms in the index?
To increase the speed of queries for frequent biwords
What is the result of using a combination scheme of frequent biwords and positional intersection?
Improved efficiency for frequent biwords
What operation takes O(m+n) time complexity in merging two postings lists?
Merging sorted lists
What is the purpose of skip pointers in postings lists?
To skip postings that will not figure in the search results
What is the tradeoff in placing skip pointers?
Between the length of skip spans and the number of comparisons
What is the advantage of using skip pointers in query processing?
Improving the efficiency of query processing
When is it possible to do better than O(m+n) time complexity in merging postings lists?
If the index isn’t changing too fast
What happens when we match a posting on both lists?
We match it and advance to the next posting on both lists
This quiz covers the basics of indexing in information retrieval, including positional and nonpositional indexes, and querying techniques.
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