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Note: Many topics at this site are reduced versions of the text in "The Encyclopedia of Networking and Telecommunications." Search results will not be as extensive as a search of the book's CD-ROM.
The Handle System is a global naming service for documents. It provides persistence for documents that might move to different locations so that users can always locate those documents, even after they have been moved. The strategy relies on uniquely identifying each document. This identity is stored in a name server along with the current location of the document. If the document is moved, the location information in the name server must be updated. When users need a document, they find it by referring to the name server.
The Handle System is a resolver service in that it resolves document names into URLs (Uniform Resource Locators), which are the actual Web site addresses where documents are stored. The Handle System provides a resolver service similar to DNS (Domain Name System), and like DNS, the Handle Service is distributed. There is a Global Handle Registry that will pass requests for documents over to local Handle services.
Assume you are writing an online report that requires a bibliographic reference. You want to hyperlink each reference so readers can quickly find them on the Web. The Handle System provides a solution. Following is an example of the kind of link you would include in your reference. This example is borrowed from Springer-Verlag, a developer of the DOI (Digital Object Identifier) system. DOI is an identification system for managing intellectual property in the digital environment. It helps link customers with publishers, facilitates electronic commerce, and enables automated copyright management:
The first part of the link is a standard Web URL that refers to the location of the DOI name server where names are resolved to actual locations. The remaining part of the link is called a "handle." The handle prefix 10.1007 identifies the publisher (Springer-Verlag, in this case), and it was assigned by the DOI agency. The handle suffix s00214990m180 identifies an actual document and is analogous to the ISBN numbers that are assigned to books.
This link can be included in any document without worry that it might fail, assuming that the administrator of the site where the actual document is located keeps the DOI name server updated about the current location of the actual document.
A unique feature of the Handle System is that handles can refer to copies of the same document at different locations. This can help balance loads when documents are in high demand or a server is too busy to handle a user request for the document.
Web sites join the global handle namespace and are assigned a unique identifier. Springer-Verlag's ID is 10.1007 in the DOI system. All documents at the site retain their current local naming scheme. The Handle System simply provides a link into that naming scheme. The administrator of the site is responsible for making sure that the Handle System links match the current document locations.
The Handle System is hierarchical. At the top is the Global Handle Registry. Below this are all "local handle services," which are usually run by organizations that have documents to publish or act on behalf of document publishers. A Web site that wishes to publish documents can join the Handle System. In doing so, it obtains a handle prefix value and becomes known as a naming authority (since it has authority over its own local namespace).
The Global Handle Registry tracks the namespace for these naming authorities so that it can divert requests to the appropriate naming authority. When a user requests a document, a query may be sent to the Global Handle Registry to find the local service that knows how to process the handle. When the Global Handle Registry finds the local service, it communicates this information to the client who then accesses the home service directly.
The Public Library Association paper called "DOI: The Persistence of Memory" provides useful information about persistent documents, including links to other relevant sites. The Web address for this document is listed on the related entries page.
A document called "Handle System Overview" was submitted to the IETF in early 2000. This document is available at the Handle System Web site listed on the related entries page.
The IETF Uniform Resource Names (URN) Working Group is defining universal resource names, which are names that remain persistent over time, even if the documents move. The URN and the Handle System may sound similar, but, in fact, the Handle System is one case of what the URN Working Group is defining. See "URN (Uniform Resource Names)" for more information.
A related technology is CIP (Common Indexing Protocol). CIP provides a way for information servers to exchange index information about the documents they hold. A server can then answer queries from its own index or look in the indexes received from other servers and make referrals to those servers. See "CIP (Common Indexing Protocol)."
Copyright (c) 2001 Tom Sheldon and Big Sur Multimedia.