Page Comparison

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1. An administrative service that manages the metadata necessary to perform naming services
2. An Admin UI to allow registered users to create and maintain URNs
3. An API that allows registered applications to interact with the administrative service without using the Admin UI
4. An HTTP-based resolution service that performs naming resolution using browser redirection
5. An API that returns information about URNs rather than resolving the URN

 
What is a persistent identifier?
What is name resolution?
Why use persistent identifiers?
What resources should be named?

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The process of creating a persistent identifier is also known as "naming" a digital resource. The majority of persistent identifiers are created for digital objects when they are deposited into the Digital Repository (DRS). Objects already stored in the DRS can be named by using the DRS Web Admin. NRS has its own Admin interface that supports naming of objects inside or outside of DRS.

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In this illustration, FHCL is Harvard College Library; RAD is Radcliffe Institute; and RAD.ARCH is Radcliffe Archives.

What is a persistent identifier?
A persistent identifier is a permanent, location-independent identifier for a network-accessible resource. Persistent identifiers are sometimes referred to as names.

In this case permanent means that once an identifier is associated with a particular resource it will never be associated with any other resource. Even if the resource itself is ephemeral and becomes inaccessible at some point in time, its persistent identifier will never be reassigned.

Location-independent means that the identifier itself does not specify the location of the resource. In order to access a resource its persistent identifier has to be resolved into a location-specific identifier such as a URL.

What is name resolution?
Name resolution is the process of mapping a persistent identifier (PID) URN to a URL that retrieves the named resource; the URL locates the resource identified by the persistent identifier:

If a resource moves or changes the way it is accessed, the mapping between the resource's persistent identifier and URL is updated; the persistent identifier remains unchanged and valid.

Why use persistent identifiers?
In general, important resources should never be directly identified by a URL because URLs can become invalid if the resource is moved or if the way it is accessed changes. (This is the cause of the "404 File Not Found" browser error message. ) By adding a layer of indirection into the access process, persistent identifiers URNs will never become invalid. If a resource moves, only the URL to which the persistent identifier URN resolves needs to be updated; the identifier URN itself can remain unchanged. As long as persistent identifiers URNs are properly maintained within NRS, 404 errors should never occur when accessing named resourcesthey should always point to the intended resource.

What resources should be named?
Digital objects intended for network delivery and accessed through OISLTS-supported delivery services, such as the Image Delivery Service (IDS) or Page Delivery Service (PDS), must be given persistent identifiers in NRS. Other objects, such as archival masters intended only for storage, can be given persistent identifiers if they meet the following criteria: