Editing Document retrieval (section)

==Description==
Document retrieval systems find information to given criteria by matching text records (''documents'') against user queries, as opposed to [[expert system]]s that answer questions by [[Inference|inferring]] over a logical [[knowledge base|knowledge database]]. A document retrieval system consists of a database of documents, a [[classification algorithm]] to build a full text index, and a user interface to access the database.

A document retrieval system has two main tasks:
# Find relevant documents to user queries
# Evaluate the matching results and sort them according to relevance, using algorithms such as [[PageRank]].

Internet [[search engines]] are classical applications of document retrieval. The vast majority of retrieval systems currently in use range from simple Boolean systems through to systems using [[statistical]] or [[natural language processing]] techniques.