Re: [netmod] regular expression flavours (again)

Hi Rob,

On Wed, 2019-06-12 at 09:25 +0000, Rob Wilton (rwilton) wrote:
> Hi Lada,
> 
> OpenConfig have already introduced a module level extension statement to
> indicate that their pattern statements use POSIX regular expressions.

What I meant was rather something like

    pattern-language "POSIX";

with the default being "XSD". It could possibly also include your proposal of
XSD regex subset (issue #21).

This could in fact be a good candidate for a critical extension.  

> 
>   extension regexp-posix {
>      description
>       "This extension indicates that the regular expressions included
>       within the YANG module specified are conformant with the POSIX
>       regular expression format rather than the W3C standard that is
>       specified by RFC6020 and RFC7950.";
>   }
> 
> Defined in 
> https://github.com/openconfig/public/blob/master/release/models/openconfig-extensions.yang
> 
> I don't think that this should become part of the YANG standard.

I suspect that developers of YANG tools are being pushed by users to include
support for this anyway, so I don't see much benefit from blocking it.

Lada

> 
> Thanks,
> Rob
> 
> 
> > -----Original Message-----
> > From: netmod <netmod-bounces@ietf.org> On Behalf Of Ladislav Lhotka
> > Sent: 12 June 2019 09:02
> > To: NETMOD WG <netmod@ietf.org>
> > Subject: [netmod] regular expression flavours (again)
> > 
> > Hi,
> > 
> > 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.
> > 
> > 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.
> > 
> > ISO Schematron adopted a similar approach with "query language binding"
> > that can be declared with the schema element, for example
> > 
> > <schema xmlns="http://purl.oclc.org/dsdl/schematron" queryBinding="exslt">
> > 
> > Any thoughts on this?
> > 
> > Lada
> > 
> > --
> > Ladislav Lhotka
> > Head, CZ.NIC Labs
> > PGP Key ID: 0xB8F92B08A9F76C67
> > 
> > _______________________________________________
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> > netmod@ietf.org
> > https://www.ietf.org/mailman/listinfo/netmod
-- 
Ladislav Lhotka
Head, CZ.NIC Labs
PGP Key ID: 0xB8F92B08A9F76C67