[Nml-wg] Identifiers

[Freek Dijkstra]

Hi all,

Last year we have had a few discussions on identifiers in the NML-WG, as
well as in the GLIF. There have been two more or less conflicting
solutions. Nevertheless, I hope to reach consensus on a way forward at
the coming OGF meeting, which coincides with the GLIF meeting.

Let me try to summarise the two points of view:
1) The theoretical view: an identifier is simply a unique string. No
information at all should be implied in it. "sdimfsdhdsjkjd39n34n58" is
great, even more if there is a good method to make it unique. E.g.
"mydomain.net:sdimfsdhdsjkjd39n34n58". The great thing is that you can
change the properties of the thing without changing the identifier.
2) The practical view: we should re-use the NURN (network identifiers)
as used in the perfSONAR software suite, e.g.
"urn:ogf:network:domain=mydomain.net:device=mydevice:port=4:link=1".
This conveniently has all the attributes inside, very easy to parse. No
need to make it more complex.

I have been an advocate of the first point of view, Martin has been a
vocal advocate of the second view. Of course, both view have their
merit. Jeff proposed to make the order of items in the perfSONAR
identifier fixed, so at least a string-wise comparison is possible
between two identifiers. Freek said he could live if the first part of
the identifier implies the originating domain.

I wonder if we can make progress by reaching consensus on the following
statements:
- The NURN is not an identifier in the formal sense, it is a couple of
properties that together uniquely identify something.
- That said, sometimes it may be overkill to create a special
identifier, but it is good enough to identify something by it's
properties, as the NURN does.
(and perhaps more controversial:)
- The identifier that is sent to external parties consists of a domain
part, identifying the originating domain, and a unique string part.
Whilst this string may contain more properties, other parties do not
need to interpret the meaning of this string.
- As the NURN is formally defined in the OGF (I presume it is in the
NM-WG), if the NML-WG deviates from this format, the NML-WG has an
obligation to also define a practical transition strategy which does not
suddenly break things.

Regards,
Freek