An Archival Resource Key is a Uniform Resource Identifier that is a multi-purpose persistent identifier for information objects of any type. An ARK contains the label ark: after the URL's hostname, which sets the expectation that, when submitted to a web browser, the URL terminated by '?' returns a brief metadata record, and the URL terminated by '??' returns metadata that includes a commitment statement from the current service provider. The ARK and its inflections provide access to three facets of a provider's ability to provide persistence. Implicit in the design of the ARK scheme is that persistence is purely a matter of service and not a property of a naming syntax. Moreover, that a "persistent identifier" cannot be born persistent, but an identifier from any scheme may only be proved persistent over time. The inflections provide information with which to judge an identifier's likelihood of persistence. ARKs can be maintained and resolved locally using open source software such as or via services such as and the central resolver.
Structure
ark:/NAAN/Name
NAAN: Name Assigning Authority Number - mandatory unique identifier of the organization that originally named the object
NMAH: Name Mapping Authority Host - optional and replaceable hostname of an organization that currently provides service for the object
Qualifier: optional string that extends the base ARK to support access to individual hierarchical subcomponents of an object, and to variants of components.
Three generic ARK services have been defined. They are described below in protocol-independent terms. Delivering these services may be implemented through many possible methods given available technology.
Access Service (access, location)
Returns the object or a redirect to the same, although a sensible object proxy may be substituted.
May also return a discriminated list of alternate object locators.
If access is denied, returns an explanation of the object's current inaccessibility.
Policy Service (permanence, naming, etc.)
Returns declarations of policy and support commitments for given ARKs.
Declarations are returned in either a structured metadata format or a human readabletext format; sometimes one format may serve both purposes.
Policy subareas may be addressed in separate requests, but the following areas should be covered:
*object permanence,
*object naming,
*object fragment addressing, and
*operational service support.
Description Service
Returns a description of the object. Descriptions are returned in either a structured metadata format or a human readable text format; sometimes one format may serve both purposes.
A description must at a minimum answer the who, what, when, and where questions concerning an expression of the object.
Standalone descriptions should be accompanied by the modification date and source of the description itself.
May also return discriminated lists of ARKs that are related to the given ARK.
