Information Retrieval
INFO 4300 / CS 4300! Indexing
– Inverted indexes
– Compression
– Index construction
– Ranking modelBut first...! Simple in-memory indexerCompression
! Inverted lists are very large– e.g., 25-50% of collection for TREC collections using
Indri search engine– Much higher if n-grams are indexed
! Compression of indexes saves disk and/or memoryspace
– Typically have to decompress lists to use them
– Best compression techniques have goodcompression ratios and
