OAIster is a crucial database/catalogue for scholars to locate online digital resources. For technical reasons many digital materials can not be indexed by search engines such as Google. Many of these materials can be found in OAIster. OAIster started as a project of the University of Michigan and has recently been taken over by OCLC. this means that OAIster is now available through the OCLC website as a separate database or as part of its Worldcat catalogue.
This is an original description of the OAIster project explaining its aims: "OAIster provides access to digital resources by "harvesting" their descriptive metadata (records) using OAI-PMH (the Open Archives Initiative Protocol for Metadata Harvesting). The Open Archives Initiative is not the same thing as the Open Access movement. Digital resources can range from an old-time advertisement of electric refrigerators (from the Library of Congress American Memory project) to Harriet Beecher Stowe memoirs (from the University of Michigan Digital Library Production Service Making of America collection). Digital resources include items such as:
These resources, often hidden from search engine users behind web scripts, are known as the "deep web." The owners of these resources share them with the world using OAI-PMH. Digital resources are often hidden from the public because a web search using a search engine like Google or Yahoo! won't be picking up information about these resources. Robots in use by such search services don't delve into the CGI that sends this resource information to the web. Consequently, these resources are generally accessible only to those who know to look in particular repositories, often at universities who are developing the collections in these repositories." See here for more information.