One key is that your first sentence implies an assumption of "persistence" just because a particular URI exists. If you don't have some policy or institutional commitment that publicly defines this then you can't say any URI is "persistent." ARKs specifically provide a mechanism to deliver object metadata and a persistence commitment statement that other redirection systems don't. The ARK specification also specifically states that "persistence" is in fact a policy commitment and a service promise and nothing else. I don't believe any other redirection service makes this claim. See NLM's permanence policy: http://www.nlm.nih.gov/psd/pcm/devpermanence.html
PID/redirection systems can provide URI opaqueness, a theory you may or may not believe in. Also, Apache-like http servers rely on directory structures; on the surface PID systems do not. This is also their mechanism for allowing you to move around or rename your storage devices and still maintain a link's persistence.
And there are way more issues, but these are some high-level notions.
John P. Rees, MA, MLIS
Archivist and Digital Resources Manager
History of Medicine Division, MSC 3819
National Library of Medicine
8600 Rockville Pike
Bethesda, MD 20894
From: Michele R Combs [mailto:[log in to unmask]]
Sent: Thursday, July 29, 2010 4:53 PM
To: [log in to unmask]
Subject: ark [was: RE: xlink:role usage]
I second the suggestions made so far, about not hard-coding the player into the <dao>.
Speaking of "ark," though, could somebody explain in plain English why or how an ark is better/worse/different than a persistent URL or URI? I've looked at a few of the sites that discuss it including https://wiki.ucop.edu/display/Curation/ARK , but I can't seem to wrap my head around what the difference is. So far as I can see it's just a URL that happens to contain the string "ark" -- surely there must be more to it than that??
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