> On 12 Jan 2017, at 22:59, Martin Bjorklund <m...@tail-f.com> wrote:
> 
> Ladislav Lhotka <lho...@nic.cz> wrote:
>> 
>>> On 12 Jan 2017, at 19:44, Juergen Schoenwaelder
>>> <j.schoenwael...@jacobs-university.de> wrote:
>>> 
>>> On Thu, Jan 12, 2017 at 09:38:46AM -0800, Andy Bierman wrote:
>>>> On Thu, Jan 12, 2017 at 9:34 AM, Juergen Schoenwaelder <
>>>> j.schoenwael...@jacobs-university.de> wrote:
>>>> 
>>>>> On Thu, Jan 12, 2017 at 09:19:54AM -0800, Andy Bierman wrote:
>>>>>> 
>>>>>> YANG statements:
>>>>>>  - It is not possible to define these statements so they are different
>>>>>> for config and oper
>>>>>>     - must
>>>>>>     - when
>>>>>>     - unique
>>>>>>     - key
>>>>>>     - min-elements
>>>>>>     - max-elements
>>>>>>     - leafref (path)
>>>>>>     - if-feature
>>>>>>     - deviation
>>>>>>     - type (or any sub-statements of type-stmt)
>>>>>>     - status
>>>>>>     - description
>>>>>>     - reference
>>>>> 
>>>>> Considering statements that constraint 'values', it is not entirely
>>>>> clear to me what they mean for state nodes. If a server has
>>>>> operational state that violates a must or range or ... constraint in
>>>>> the YANG model, what is the server expected to do?
>>>>> 
>>>> 
>>>> The client uses the YANG validation to check on what the server is
>>>> sending.
>>>> The server is buggy if it is sending data that violates YANG
>>>> constraints.
>>>> If any of these statements need to be different for config and oper
>>>> then the old style YANG has to be used instead.
>>>> 
>>> 
>>> OK. So the client does the validation. What does the client do if the
>>> operational state it got is not valid according to the YANG
>>> constraints?
>> 
>> Don't forget that data models also provide guidelines to server
>> implementors.
> 
> Yes, and that it is all that can be done currently.  I don't think any
> implemention that receives a <get> request today freezes the system in
> order to get a guaranteed consistent snapshot.  Instead, the different

Which doesn't mean that inconsistent (format of) state data is acceptable. My 
colleague develops a BGP looking glass, and it is really a terrible work 
because he has to do a lot of screen-scraping. Each time a vendor changes the 
data format, he has to update his software. I keep telling him that our nice 
protocols would save him from this drudgery.

Lada

> subsystems will be queried, sequentially or in parallell, and the end
> result is shipped to the client.  The result may or may not be
> consistent.
> 
> 
> /martin

--
Ladislav Lhotka, CZ.NIC Labs
PGP Key ID: 0xB8F92B08A9F76C67





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