Retrieval classification

The tool often used in traditional literature retrieval is the index card, which records the information of literature on the index card. The index card generally records the title, author, subject words, abstract and other information of the literature.

When looking for a document, you should first check the index and find the location of its collection, and then ask for information. In the network age, we are looking for it all the time. There are two main ways to search on the Internet: directory browsing and using search engines.

The way to browse the directory is the way used by Yahoo search engine. Users can click on the directory according to their own needs, go deep into the next subdirectory and find the information they need. This method is convenient to find a certain kind of information set, but the ability of accurate positioning is not strong.

Search engine is the most commonly used network retrieval tool at present. Users only need to submit their own requirements, and search engines can return a large number of results. These results are ranked according to their relevance to the search question.

In addition to search engines, various databases ordered by libraries are also important ways of information retrieval. Thomas mann, a reference librarian of the Library of Congress, introduced some retrieval methods such as keyword retrieval, citation retrieval and relevance retrieval.