Re: [netmod] regular expression flavours (again)

"Rob Wilton (rwilton)" <rwilton@cisco.com> Wed, 12 June 2019 09:25 UTC

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From: "Rob Wilton (rwilton)" <rwilton@cisco.com>
To: Ladislav Lhotka <lhotka@nic.cz>, NETMOD WG <netmod@ietf.org>
Thread-Topic: [netmod] regular expression flavours (again)
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Date: Wed, 12 Jun 2019 09:25:38 +0000
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Archived-At: <https://mailarchive.ietf.org/arch/msg/netmod/v63R5GvA8pqqmgyIg4m2-HdzeAs>
Subject: Re: [netmod] regular expression flavours (again)
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Hi Lada,

OpenConfig have already introduced a module level extension statement to indicate that their pattern statements use POSIX regular expressions.

  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.

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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