The WorldCat online federated directory database is the world's largest bibliographic record database, containing bibliographic records and collection information of OCLC's nearly 20,000 member libraries. Since its establishment in 1971, it has included a total of 486 languages and a total of more than 320 million unique bibliographic records and more than 2.1 billion collection records. Each record contains collection information, which basically presents the books and other materials owned by libraries around the world from 4,800 years AD to present. There are a variety of literature types, including books, manuscripts, maps, web sites and web resources, musical scores, video materials, newspapers, periodicals and magazines, articles, and archives. The database is updated every ten seconds on average.