Data expansion:
Retrieval is a Chinese vocabulary, and the pinyin is Ji m 4 n su ǒ, which refers to finding out relevant information from a specific information set according to certain clues and rules, using certain methods and technical means.
Search and search synonyms. Nowadays, the word "search" can be seen as a directory in the format given in many bidding documents. At the same time, it is intended for the bidder to prepare the required information according to the requirements of the tender documents for the tenderer's reference.
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. 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.
The so-called retrieval effect refers to the effectiveness of the retrieval system, which is manifested in the ability of the retrieval system, including technical and economic effects. The most commonly used retrieval evaluation indicators are recall rate R (recall rate) and precision rate P (precision rate). R= the number of relevant documents retrieved/the total number of relevant documents in the retrieval system. P= number of related documents detected/total number of documents detected.