Magazine article Computers in Libraries

Ark

Magazine article Computers in Libraries

Ark

Article excerpt

primer: ARK

Acronym:

ARK

What it stands for:

Archival Resource Key

What is its purpose?

The ARK naming scheme is designed to facilitate the high-quality and persistent identification of information objects. A founding principle of the ARK is that persistence is purely a matter of service and is neither inherent in an object nor conferred on it by a particular naming syntax. The best that an identifier can do is to lead users to the services that support persistence. The term ARK itself refers both to the scheme and to any single identifier that conforms to it.

An ARK is a special kind of URL that connects users to three things: the named object, its metadata, and the provider's promise about its persistence. When entered into the location field of a Web browser, the ARK leads the user to the named object. That same ARK, followed by a single question mark ('?'), returns a brief metadata record that is both human- and machine-readable. When the ARK is followed by dual question marks ('??'), the returned metadata contains a commitment statement from the current provider.

Unlike the URN, DOI, and PURL schemes, the ARK scheme recognizes that two important classes of name authority affect persistence: original assigners of names and current providers of mapping services (which map names to objects, to metadata,and to promises). Over time, the original assigner (the Name Assigning Authority) and its policies increasingly have less to do with the current providers (the Name Mapping Authorities) and their policies. There may be many mapping authorities at once, and many in succession.

Here is an example illustrating the structure of an ARK:

The part of the ARK before the NAAN plays no part in identifying the object or in comparing ARKs for equivalence; it only serves to make the ARK actionable. The NMAH part is temporary, disposable, and replaceable. It is thus a kind of identity-inert, disposable booster rocket that launches the ARK into Cyberspace while allowing for limited branding. When the Web no longer exists, the core identity of the ARK is easily recovered by isolating the part of the ARK that begins with "ark:/".

The following ARKs are synonyms for the same object:

http://foobar.zaf.org/ark:/12025/654xz321

http://sneezy.dopey.com/ark:/12025/654xz321

ark:/12025/654xz321

A carefully chosen hostname in the NMAH could last for decades. If the NMAH ever fails, the ARK specification describes a look-up algorithm for finding a new NMAH for the object. The algorithm is essentially a simplification of the original URN resolver discovery algorithm that uses Domain Name System (DNS) Naming Authority Pointer records. …

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