[Nsi-wg] [Nml-wg] NML Topology identifiers

[Freek Dijkstra]

Henrik,

As for the adding hierarchy to URNs, I suggest we discuss this at OGF
40. I think it is a bad idea to add a network hierarchy to an
identifier, but do not necessarily object to all sorts of hierarchies.
In fact, the URN:OGF:NETWORK specification already requires that the
first part of a URN starts with an identifier of the assigning
organization (which is somewhat akin to the NSA, but not necessarily the
same as the Topology).


As for dropping the date part in the URN, please read GFD 202, section
5. http://www.ogf.org/documents/GFD.202.pdf

The date is there for a reason: ensuring persistent uniqueness, without
creating a registry.

Adding 5 bytes seems like a cheap cost compared to any alternatives.


On 11-12-2013 13:56, Jeroen van der Ham wrote:

> John has dug up references of use of URNs where it is allowed to
> analyze the structure of the identifiers and to interpret that.

It's allowed by URN specs, but quite strongly discouraged by the URN
community.

Subdelegations of the URN specs may add further restrictions (such as
the requirement that an identifier is context-free, and may only be
interpreted by the assigning organisation), and that is what GFD 202 did.


The eye-opener for me was the following email:
http://www.ietf.org/mail-archive/web/urn/current/msg01564.html

I'll quote verbatim:

> if you allow people to assign URNs as they prefer, they always tend
> to "invent" some semantic rules.
> 
> At the end you have your database full of Identifiers like:

> [institution-name]-[division-name]-[collection-name]-[date]-[item-number]
>
>  This goes fine many years.

> Till the day the collections are renamed or two divisions fusion
> under another name or renaming of the institution or ...
> 
> Experiences like those are the reason why many colleagues with Long
> Term Archiving background propagate Identifiers without semantics
> --meaningless strings just for machines.

I was Brainwashed too, and I now also propagate identifiers without
semantics. :)

Freek

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Freek Dijkstra
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