Information retrieval systems use indexes and inverted indexes to quickly search large document collections by mapping terms to their locations. Boolean retrieval uses an inverted index to process Boolean queries by intersecting postings lists to find documents that contain sets of terms. Key aspects of information retrieval systems include precision, recall, and ranking search results by relevance.

1. Boolean retrieval

6. term-document incidence matrix

12. ・ The sequence of terms in each document is sorted alphabetically ・ Instances of the same term are then grouped by word and then by documentID ・ The terms and documentID are then separated out ・ The dictionary stores the terms, and has pointer to the postings list for each term

14. Algorithm for the intersection of two postings lists p1 and p2.

15. For complex queries