HDL® Identifier and Resolution Services
The Handle System® is an infrastructure on which applications serving many different purposes have been built. Among the objects we know of that are identified by handles are journal articles, technical reports, books, theses and dissertations, government documents, large scientific data sets, movie and television assets, and distributed learning content. HDL identifiers are being used in digital watermarking applications, GRID applications, repositories, registries and more.
There are six service sites comprising the Global Handle Registry®. Those services, and those proxy servers that are known to CNRI that pass requests to the system from the web, receive approximately 200 million resolution requests per month.
There are thousands of handle services running today, located in 75 countries, on 6 continents; more than 1,000 of them are at universities and libraries. Handle services are being run by user federations, national libraries, national laboratories, universities, computing centers, national and local government agencies, contractors, corporations, and research groups.
The number of prefixes, which allow users to assign handles, is growing and exceeds 13,000.
The International DOI Foundation's implementation of handles, the DOI® System, has More than 100 million registered handles.
The Handle System infrastructure is supported by prefix registration and service fees. The majority of those fees come from single prefix holders. Among the largest users and contributors is the International DOI Foundation.
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