[tdwg-content] Why UUIDs alone are not adequate as GUIDs, was Re: ITIS TSNID to uBio NamebankIDs mapping [SEC=UNCLASSIFIED]

Paul Murray pmurray at anbg.gov.au
Thu Jun 9 04:56:15 CEST 2011

On 08/06/2011, at 8:05 AM, Steve Baskauf wrote:

> ... I think it's foolish to regard all of these different
> resolution mechanisms as distinct "identifiers".  There is *ONE* GUID.  It
> is: A9F435E0-8ED7-46DD-BAB4-EA8E5BF41523.  There are ten different ways to
> make it actionable. It therefore meets the recommendations of the
> applicability statement.
> The problem is that when you create an HTTP URI out of a UUID, you are creating an identifier whether you think you are or not. 

Jumping in again, but perhaps RFC 4122 might help a little here.

A GUID (or UUID) is a set of 128 bits, 16 octets, 32 hex digits, 5 inches of punched paper tape. However you choose to write or express it, there is indeed "*ONE* GUID".

A URI is not a GUID. This:

is a different URI to this

is a different URI to this:

Furthermore, these uris have nothing whatever to do with the guid - apart from the fact that it's obvious to we humans that they do.

Fortunately, there is a standard for expressing a guid/uuid as a URI, and it is the "uuid" urn namespace, defined in RFC-4122. Thus:


is a URI that - according to a w3c standard - corresponds to the 128-bit guid. This:


is *not valid* - it doesn't conform to the schema. There is one unique (case insensitive) uuid urn for any guid, and a defined equivalence between them. These are not "cool uris", but guids are inherently uncool so that's to be expected.

If you want to use GUIDs for identifiers and need equivalent URIs (for use in RDF and the semweb), then urn:uuid:<the guid> might be a good way to go.

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