A survey of alternative designs for a search engine storage structure

Abstract

Three information retrieval storage structures are considered to determine their suitability for a World Wide Web search engine: The Wolverhampton Web Library — The Next Generation. The structures are an inverted file, signature file and Pat tree. A number of implementations are considered for each structure. For the index of an inverted file a sorted array, B-tree, B+-tree, trie and hash table are considered. For the signature file vertical and horizontal partitioning schemes are considered and for the Pat tree a tree and array implementation are considered. A theoretical comparison of the structures is done on seven criteria that include: response time, support for results ranking, search techniques, file maintenance, efficient use of disk space (including the use of compression), scalability and extensibility. The comparison reveals that an inverted file is the most suitable structure, unlike the signature file and Pat tree, which encounter problems with very large corpora.