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Can I use UUID's with ARK?

· 2 min read
Bob Coret

Yes, although hyphens have no meaning in the Assigned Name of an ARK, you can use UUID's as Assigned Names in ARK, the local resolver does need to be made aware.

ARK name strings​

Within ARK, the Assigned Name (basically the object identifier) ​​is bound to certain rules, which are explained on the Running minters and resolvers page. These rules boil down to:

digits, letters (ASCII, no diacritics), and the following characters: = ~ * + @ _ $ . /

But there's also the following:

Another unique feature of ARKs is that hyphens (‘-‘) may appear but are identity inert, meaning that strings that differ only by hyphens are considered identical; for example, these strings:

  • ark:12345/141e86dc-d396-4e59-bbc2-4c3bf5326152
  • ark:12345/141e86dcd3964e59bbc24c3bf5326152

identify the same thing.

UUIDs​

The 'identity inert' feature paves the way to use UUIDs for Assigned Names, which according to the ABNF in RFC 9562 Universally Unique IDentifiers (UUIDs) must conform to:

UUID     = 4hexOctet "-"
           2hexOctet "-"
           2hexOctet "-"
           2hexOctet "-"
           6hexOctet
 hexOctet = HEXDIG HEXDIG
 DIGIT    = %x30-39
 HEXDIG   = DIGIT / "A" / "B" / "C" / "D" / "E" / "F"

BTW, the RFC also states:

Note that the alphabetic characters can all be uppercase, lowercase, or mixed letters,

So, as heritage organisation (and as Collection Information System vendor), you can certainly use a UUID for the Assigned Names part of your persistent HTTP URIs.

Resolvers​

However, in the realm of resolvers, you will need to consider the fact that the hyphen has no meaning. The nt2.net and arks.org resolvers chose an implementation where the hyphen is removed from the Assigned Names "as they have no meaning." upon redirect.

In practice, for heritage organisations using UUID's the local resolver (on the heritage institution's side) will have to redirect (*)/interpreted an ARK like ark:12345/141e86dcd3964e59bbc24c3bf5326152 as/to ark:12345/141e86dc-d396-4e59-bbc2-4c3bf5326152. This Assigned Name 'in UUID style' can then simply be routed to the object page or - based on content negotiation - resolved to RDF information.

*) Example Apache rewrite rule with regexp:

RewriteRule ^ark:([0-9]+)/([0-9a-fA-F]{8})([0-9a-fA-F]{4})([0-9a-fA-F]{4})([0-9a-fA-F]{4})([0-9a-fA-F]{12})$ /ark:$1/$2-$3-$4-$5-$6 [R=301,L]