Inverted Indexes


If one considers a magazine article to be a document, then an issue of the magazine constitutes a corpus—it is a collection of one or more documents.

An index maps the salient information in a corpus into a format designed to let you quickly locate specific content. Each entry in an index points you to one or more articles. You can think of an index as a list of terms, with each term followed by a list of the documents it appears in.

This sort of index, the one that people usually think of, is formally known as an inverted index.

The term “inverted” refers to the arrangement of information in the index, which is intended to locate documents by matching on terms. This is “inverted” compared to using documents directly: if you pick up a book, you “match” on the document and “locate” all the terms in it.




      “There are no ordinary moments.”    
      ― Dan Millman, Way of the Peaceful Warrior: A Book That Changes Lives