Re: [NGO] WG Review: NETCONF Data Modeling Language (netmod)

Phil Shafer <> Mon, 21 April 2008 15:58 UTC

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To: Chris Newman <Chris.Newman@Sun.COM>
Subject: Re: [NGO] WG Review: NETCONF Data Modeling Language (netmod)
In-reply-to: <D50248ED6D20DB444FD88CD1@446E7922C82D299DB29D899F>
Date: Mon, 21 Apr 2008 08:41:13 -0400
From: Phil Shafer <>
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Chris Newman writes:
>The simpler (5) 
>happens to be, the more confident I will become that YANG is following best 
>practices for XML DMLs.

My guess is the opposite:  many of the more useful features of XSD
and DSDL require distinct and uncomfortable layout of the schema
material.  For example, the XSD substitution group mechanism allows
for extensibility, but requires the schema to include substitution
group information pervasively throughout the schema and to make a
very shallow hierarchy through the use of types and indirection.
This gives a format that I believe non-validating consumers of the
schema will find difficult to read and use.

By contrast, YIN is a straight-forward conversion of the textual
data from a YANG module into an XML format that can be easily and
directly used by the consumer.  The conversion is trivia and the
information is in a state identical to the YANG module's layout.
The encoding is changed (to XML) but the content is untouched.

So if (5) is simple, we've either chosen not to use significant but
uncomfortable features in the low-level output language, or we've
lost the conciseness, hierarchical view, and other high-level features
that makes YANG worthwhile.

This isn't to say that (5) shouldn't be fairly mechanical, something
that a perl or xslt script could handle, but it shouldn't be called
simple, nor should the complexity of that transformation a basis
for judging YANG.

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