What is Signature File

In this chapter, we discuss an efficient and effective index mechanism for search engines to support both conjunctive and disjunctive queries. The main idea behind it is to decompose an inverted list into a collection of disjoint sub-lists. We will associate each word with an interval sequence, which is created by applying a kind of tree coding to a trie structure constructed over all the word sequences in a database. Then, attach each interval, instead of a word, with an inverted sub-list. In this way, both set intersection and union can be conducted by performing a series of simple interval containment checks. Experiments have been conducted, which shows that the new index is promising. Also, how to maintain indexes, when inserting or deleting documents, is discussed in great detail.