[Please post counter proposals also to
https://forge.ogf.org/sf/go/artf6495]

I have recently distributed some NML example topologies to people
outside of the NML developers. This included label definitions like:

 <nml:label>
   <nml:parameter
name="type">http://schemas.ogf.org/nml/2013/10/ethernet/vlan</nml:parameter>
   <nml:parameter name="values">1780-1783</nml:parameter>
 </nml:label>


Some of the feedback was that the label syntax was too verbose, and the
alternative was akin to the original proposal:

 <nml:label
labelType="http://schemas.ogf.org/nml/2013/10/ethernet/vlan">1780-1783</nml:label>

This in combination with a recent majority on the NML mailing list who
favoured a relative flat syntax for label ranges ("1780-1783" instead of
<start>1780</start><end>1783</end>) has prompted me to see if a more
simple alternative is possible. To that end, I posed two complex label
definitions, to see how those can be described:


1. IP does not describe resource labels, but a source + destination
label pair. How to describe a label pair with "source IP 145.100.124.38
and destination IP 193.10.252.66"?

2. WDM channel not only have a (central) frequency (or central
wavelength) but also a given frequency bandwidth, the spacing. How to
specify the these (ITU-gridless) wavelengths: "The wavelengths with
193.0, 193.1 and 193.2 central frequency with 100 GHz spacing, and
another wavelength at 193.275 central frequency with 50 GHz spacing".


After some thinking, here is a proposal:
(sorry for the quoting, this prevents wrapping in my mail client)

1. <nml:label labeltype="http://schemas.ogf.org/nml/2013/10/ip/ipv4"><source>145.100.124.38</source><destination>193.10.252.66</destination></nml:label>

2. <nml:labelgroup labeltype="http://schemas.ogf.org/nml/2013/10/dwdm/frequency">193.0-193.2±0.05,193.275±0.025</nml:label>

  (or the alternative if we don't want a non-ASCII "±" sign, and like to see the spacing rather than half the spacing):

  <nml:labelgroup labeltype="http://schemas.ogf.org/nml/2013/10/dwdm/frequency">193.0-193.2~0.1,193.275~0.05</nml:label>

In conclusion, I think that the shorter variant can be done, as long as
we specify per labeltype what the syntax is. I recommend to distinguish
between nml:label and nml:labelgroup, now that the
type="value"/type="values" is no longer there to distinguish between a
label and a label group.

Regards,
Freek
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