American MemoryThe National Digital Library Program: Archived Documentation

The Library of Congress / Ameritech National Digital Library Competition (1996-1999)

Handle Server [May 4, 1998]

Overview   |   More on Handles and Naming Authorities   |   A Global System of Handle Servers

Any form of Uniform Resource Name (URN) has three properties:

  1. Location independence -- not tied to a particular computer
  2. Persistence -- long-term validity
  3. Global uniqueness
The CNRI Handle System provides support for a naming scheme with these properties. Handles have the form:
URN:hdl: naming authority / name

Handles are independent of location

Today's WWW browsers use Uniform Resource Locators which point to files on particular computers. A browser (or any other computer program) that supports URNs will present a location-independent URN to a URN server for resolution into a URL or some other form of locator. CNRI has developed software for a Handle System, which is being incorporated into some prototype digital libraries, including a prototype repository for American Memory. When a resource is moved, its record in the handle server is modified. Users of the handle will be unaware of the move. Links to the handle will automatically access the resource from its new location.

Handles are persistent

In comparison with some other candidate schemes for Uniform Resource Names, the CNRI system emphasizes persistence. There is no formal relationship between the scheme's naming authorities and existing network-related names such as Internet domain names, which may change if two publishers merge. Once an item has been named by an authority, its handle can be permanent. The naming authority can move its operations across the country or round the world without a need to alter handles. If an authority goes out of business and ceases to create new handles, the handles it had registered can remain in the system.

Handles are unique

The Global Handle Registry will not permit the creation of duplicate naming authorities. Whenever a naming authority creates a new handle, the handle is checked for uniqueness.

Related reading from outside the Library of Congress:

NOTE: Links to resources outside the Library of Congress are to URLs that were active when this set of archived documentation was actively maintained. Some links may no longer be active because resources have been removed. If a link is active, the resource may have changed substantially since the documentation was created. No attempt will be made to trace the linked resources or to suppress bad links. The URLs are being retained for their value as historical evidence.

Key Concepts in the Architecture of the Digital Library, William Y. Arms, D-Lib Magazine, July 1995. (hdl:cnri.dlib/july95-arms.html).

In this article, based on a presentation at the April 1995 meeting of the Coalition of Networked Information (CNI), Bill Arms of CNRI introduces the handle-server and repository in simple terms and diagrams.

Handle System Overview: Version 4.0.

CNRI's web pages for Handles and the Handle System.
[At ].

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