Overview

The Name Resolution Service (NRS) is a Harvard Library service for creating, maintaining, and resolving URNs, also called persistent identifiers or Names. URNs are location-independent names for network-accessible resources. "Name Resolution" is the process of converting a URN into the URL to the resource. If a resource's URL changes, the mapping between the resource’s URN and URL can be updated; the URN itself, however, remains unchanged and valid. By using URNs, curators and researchers can cite a URL that will always point to the same resource. If the resource itself becomes unavailable at some future time, the URN will never point to a different resource.

The NRS has several components:

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

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

Who can use NRS?

Any Harvard administrative organization is eligible to use NRS.

How are persistent identifiers created?

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.

What is a Naming Authority? What is an Authority Path?

Every URN in NRS has to be unique. In order to give groups at Harvard the most flexibility in creating unique URNs, groups are given control over a set of URNs that begin with a specific set of characters. A Naming Authority is the set of characters an administrative unit uses to create URNs. Groups can create child Naming Authorities in a hierarchical tree structure to further split up a Naming Authority. URNs display the parent child relationships by using a period between the parts. For instance, URN-3:RAD is a parent Naming Authority, and URN-3:RAD.ARCH is a child Naming Authority.

The root naming authority in NRS (URN-3) is administered by LTS. LTS has established a number of top-level naming authorities under URN-3 that correspond to Harvard schools or administrative units:

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

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

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. By adding a layer of indirection into the access process, URNs will never become invalid. If a resource moves, only the URL to which the URN resolves needs to be updated; the URN itself can remain unchanged. As long as URNs are properly maintained, they should always point to the intended resource.

What resources should be named?
Digital objects intended for network delivery and accessed through LTS-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:

The object represents a complete intellectual work, either an atomic work such as an image or a sound file, or an aggregate work such as a multi-page volume. In general, individual components of an aggregate work that have little or no contextual meaning separate from the aggregate, such as a single page of a volume, should not be given persistent identifiers.

Web links to the object will be established and distributed.

The object's location can be tracked and maintained reliably.

The object possesses sufficient intellectual or curatorial value as to warrant the permanent maintenance of the persistent identifier.

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