Re: [netmod] regular expression flavours (again)

[Juergen Schoenwaelder <[e-mail]>]

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.

> 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.

/js

-- 
Juergen Schoenwaelder           Jacobs University Bremen gGmbH
Phone: [phone]         Campus Ring 1 | 28759 Bremen | Germany
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