Re: [netmod] yang canonical integer format

Ladislav Lhotka <lhotka@nic.cz> Mon, 06 March 2017 12:28 UTC

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From: Ladislav Lhotka <lhotka@nic.cz>
To: Robert Varga <nite@hq.sk>, Kent Watsen <kwatsen@juniper.net>, Juergen Schoenwaelder <j.schoenwaelder@jacobs-university.de>, "netmod\@ietf.org" <netmod@ietf.org>
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Date: Mon, 06 Mar 2017 13:28:16 +0100
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Subject: Re: [netmod] yang canonical integer format
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Robert Varga <nite@hq.sk> writes:

> Hello,
>
> On 03/03/2017 05:52 PM, Kent Watsen wrote:
>>>  typedef ether-type {
>>>    type uint16 { format "%x"; }
>>>  }
>>>
>>> in plain YANG to make the hexadecimal format the canonical format. Who
>>> maintains ideas for the next YANG revision?
>
> This is also useful for other types, for example inet-types:mac-address,
> where implementations could use an 'canonical-pattern' type of
> declaration.

Perhaps even more common use case would be IP addresses - an IPv4 address
is basically a uint32 represented as a dotted quad.

>
> I think this particular idea ties the transport-specific representation
> to a type definition -- I mean requiring binary transports to send
> uint16s as text is not efficient and they would end up not using the
> statement at all. This is also sticky if the transport places additional
> restrictions on what is and is not a valid string and reminds me of some
> of the 'anyxml' problems...

DSDL has "extensible datatypes" [1] that try to approach this problem
from the other end: a type may provide a recipe (regular expression +
XPath transformation) for parsing a string into the "internal" value.

BTW, DSDL seems to be dead as dodo, even the dsdl.org domain now
advertises some Danish online gambling. :-) This is sort of pity, they
had quite a few interesting ideas.

Lada

[1] http://conferences.idealliance.org/extreme/html/2006/Tennison01/EML2006Tennison01.html

>
>>>
>>> /js
>> 
>> Ideas for the next revision of YANG are being captured in this tracker:
>> 
>>   https://github.com/netmod-wg/yang-next/issues
>> 
>
> given YANG is an extensible language, would it make sense to deliver
> these outside of YANG revisions?
>
> The main reason for doing so is that these, unlike YANG revisions:
> - do not change the meta model of the language
> - are not mandatory-to-implement
>
> It will also allow for faster delivery to end users.
>
> Regards,
> Robert
>
> _______________________________________________
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> netmod@ietf.org
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-- 
Ladislav Lhotka, CZ.NIC Labs
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