Re: WG Review: NETCONF Data Modeling Language (netmod)

"Tom.Petch" <> Thu, 24 April 2008 08:37 UTC

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From: "Tom.Petch" <>
To: "David Harrington" <>, "'Eric Rescorla'" <>, "'Bert Wijnen - IETF'" <>
References: <><><> <013b01c8a559$91a23be0$>
Subject: Re: WG Review: NETCONF Data Modeling Language (netmod)
Date: Thu, 24 Apr 2008 09:22:22 +0200
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----- Original Message -----
From: "David Harrington" <>
To: "'Eric Rescorla'" <>om>; "'Bert Wijnen - IETF'"
Cc: <>rg>; <>
Sent: Wednesday, April 23, 2008 5:49 PM
Subject: RE: WG Review: NETCONF Data Modeling Language (netmod)

> > -----Original Message-----
> > From: [] On
> > Behalf Of Eric Rescorla
> > > I propose that you list (again) your (technical) objections
> > > to the the current proposal.
> >
> > Sure. Based on my knowledge of modelling/protocol description
> > languages, the techniques that Rohan described based on RNG and
> > Schematron seemed to me quite adequate to get the job done and the
> > relatively large baggage introduced by defining another language
> > (YANG) which is then translated into them seems wholly unnecessary.
> >
> > I appreciate that some people believe that YANG is more expressive
> and
> > better suited for this particular purpose, but I didn't see any
> really
> > convincing arguments of that (I certainly don't find the arguments
> in
> > F.2 of draft-bjorklund-netconf-yang dispositive). Given what I know
> of
> > the complexity of designing such languages, and of their ultimate
> > limitations and pitfalls, this seems like a bad technical tradeoff.
> The people who believe that YANG is more expressive and better suited
> for this poarticular purpose include contributors to the design of
> SMIv2, MIB Doctors, members of the NMRG who helped develop the SMING
> information and data modeling language,  contributors to the SMIng WG
> which worked on developing a proposed SMIv3 to converge the SMIv2
> standard and the SPPI data modeling language standard and the NMRG
> SMING approach, and engineers who have multiple independent
> implementations of running code for Netconf data modeling.

Sounds magnificent but who are these people and where are they?

I do track the YANG and NGO mailing lists and what I see there worries me.  I
see a significant number of questions along the lines; of what does this mean,
how can this ever work, how can I do ... and the questions are all very
reasonable and need answers - which they mostly get, even if they are somewhat
too often along the lines of 'oh dear', or 'more work needed'.

But they are the sort of questions I, for all I have done with SMI, ASN.1 and
other languages, would not have thought to ask; they come from someone at the
sharp end writing code for today's boxes.  Yet these questions are almost all
coming from just one person with a specific market place, and if he can find so
many doubts and queries, how many more are there waiting to be discovered?

That one person - hi, Andy! - is doing a magnificent job but for a new language
to live up to its billing, we need half a dozen such people, from different
parts of O&M to find the holes; and I just do not see them, at least not on the
YANG and NGO mailing lists.

The answers, likewise, mostly come from the same three or so people; again, I am
concerned that there are not more, given the claims of yang.

This causes me to doubt that we, the IETF, really has the community of interest
to undertake such a challenging assignment.

Tom Petch


> David Harrington
> _______________________________________________
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