<P> An object is an entity that is represented by information in a content collection or database . User queries are matched against the database information . However, as opposed to classical SQL queries of a database, in information retrieval the results returned may or may not match the query, so results are typically ranked . This ranking of results is a key difference of information retrieval searching compared to database searching . </P> <P> Depending on the application the data objects may be, for example, text documents, images, audio, mind maps or videos . Often the documents themselves are not kept or stored directly in the IR system, but are instead represented in the system by document surrogates or metadata . </P> <P> Most IR systems compute a numeric score on how well each object in the database matches the query, and rank the objects according to this value . The top ranking objects are then shown to the user . The process may then be iterated if the user wishes to refine the query . </P> <Table> <Tr> <Td> "</Td> <Td> there is...a machine called the Univac...whereby letters and figures are coded as a pattern of magnetic spots on a long steel tape . By this means the text of a document, preceded by its subject code symbol, ca be recorded...the machine...automatically selects and types out those references which have been coded in any desired way at a rate of 120 words a minute </Td> <Td>" </Td> </Tr> <Tr> <Td_colspan="3">--J.E. Holmstrom, 1948 </Td> </Tr> </Table>

Retrieval of information from a computer is called