Subject: [netmod] draft-ietf-netmod-rfc6087bis-13 - section 4.26.2

From: "Bogaert, Bart (Nokia - BE/Antwerp)" <[email-masked]>
Date: Mon, 28 Aug 2017 10:39:50 +0000

I would like to understand why the YANG 1.1 feature logic is *much more
expensive* than YANG 1.0.  As far as I can see the way YANG features are
being defined has not changed between YANG 1.0 and YANG 1.1.

On the other hand, the second paragraph of this section seems to deal with
"when" versus "if-feature" and the preference to use if-feature instead of
when, if possible.  But as far as I'm aware there are no changes w.r.t. when
between YANG 1.0 and YANG 1.1.  This paragraph seems to suggest that "when"
is worse than if-feature.  I can understand that when is to be evaluated and
depends on the when-condition while a feature can be considered as a design
and implementation choice (the feature is supported or not) and does not
need any run-time 'validation'.  But why is this so different in YANG 1.1
versus YANG 1.0?

Where can we find more background on the statement made in this section
about much more expensive and what exactly is meant by this, certainly when
we want to see this in the perspective of the run-time characteristics and
impact on a NC server running in a device.

Thanks in advance,

Bart

---

From: Martin Bjorklund <[email-masked]>
Date: Mon, 28 Aug 2017 13:11:40 +0200 (CEST)

Hi,

"Bogaert, Bart (Nokia - BE/Antwerp)" <[email-masked]> wrote:
> expensive* than YANG 1.0.

The document says "much more _expressive_".

> As far as I can see the way YANG features are

if-feature can in YANG 1.1 be a boolean expression of features, e.g.,
"foo or bar and not baz".

> need any run-time 'validation'.  But why is this so different in YANG 1.1

This was true also in 1.0 (i.e., 'if-feature' is simpler than 'when')

/martin

---

From: "Bogaert, Bart (Nokia - BE/Antwerp)" <[email-masked]>
Date: Mon, 28 Aug 2017 11:37:39 +0000

-----Original Message-----
From: Martin Bjorklund [mailto:[email-masked]] 
Sent: Monday, August 28, 2017 1:12 PM
To: Bogaert, Bart (Nokia - BE/Antwerp) <[email-masked]>
Cc: [email-masked]
Subject: Re: [netmod] draft-ietf-netmod-rfc6087bis-13 - section 4.26.2

Hi,

The document says "much more _expressive_".
[Bart Bogaert] Oops... need to have my eyes checked...  thanks for pointing
out.

Regards, Bart