Re: [netmod] regular expression flavours (again)

[Ladislav Lhotka <[e-mail]>]

On Wed, 2019-06-12 at 11:25 +0200, Juergen Schoenwaelder wrote:
> On Wed, Jun 12, 2019 at 10:01:30AM +0200, Ladislav Lhotka wrote:
> 
> > I think it is very unfortunate that OpenConfig folks use POSIX regular
> > expressions instead of XSD. This of course causes confusion, see e.g. this
> > PR:
> > 
> > https://github.com/CZ-NIC/yangson/pull/22
> > 
> > Given the popularity of OpenConfig models, it seems to me that it would be
> > better if YANG somehow accomodates such (largely cosmetic) differences.
> 
> The differences are not cosmetic. See previous discussions on this topic.

What I meant is that such differences are still relatively easy to handle,
unlike e.g. the schema structure that is incompatible with the current
conventions and NMDA.

> 
> > One option would be that each YANG module declares the regex flavour used in
> > its
> > patterns. Yes, it is a complication, but having separate forks of YANG is
> > much
> > worse.
> 
> It is sad that OpenConfig does not follow the standard. If OpenConfig
> can't live without POSIX regular expressions, then OpenConfig should
> have used proper extension statements instead of simply changing the
> semantics of the YANG pattern statement to measn something
> different. That said, they do seem to declare something like
> oc-ext:regexp-posix; but it would have been much smarter to use for
> example oc-posix:regex instead of changing the semantics of the
> pattern statement.
> 
> I would rather see OpenConfig adopting the standard or fixing their
> POSIX regular expression solution so that it avoids changing the
> semantics of YANG statements. Having statements mean different things
> depending on some context is pretty bad design.

I agree with all this but, apparently, OpenConfig people don't care too much.
And since they are much more agile than the IETF, our views may soon become
irrelevant.

Lada

> 
> /js
> 
-- 
Ladislav Lhotka
Head, CZ.NIC Labs
PGP Key ID: 0xB8F92B08A9F76C67