[NGO] Re: [YANG] YANG augment-stmt

[Balazs Lengyel <[e-mail]>]

Hello,
Certainly some uses of augment could be really confusing, so if we could restrict it without 
ugly CLRs to the two use-cases it would be nice. Something like either use top level augment or 
an augment augmenting direct siblings like in Martin's example?
Imagine an augment within an augment both with a dynamic when condition or an augment within a 
choice etc.
Balazs

Martin Bjorklund wrote:
> Andy Bierman <[e-mail]> wrote:
>> Hi,
>>
>> Looking at the ABNF for the all-powerful augment statement,
>> I notice it can appear inside a list or inside an another augment,
>> anywhere a data-def-stmt can go in fact.
>>
>> Since this clause does not instantiate any data where it
>> located, but rather at the target specified by the augment-arg-str,
>> the containment for the augment seems pretty much irrelevant,
>> except that the augment could be nested within N different 'when'
>> statements, nested inside obsolete nodes, etc.
>>
>> The key in a list with an augment-stmt has no affect on the target data,
>> does it?
> 
> I'm not sure I understand this question.
> 
>> What does it mean to have an augment inside a grouping, so that
>> it is copied everywhere a 'uses' for that grouping is specified?
>>
>> What is the use-case for augment inside augment?
> 
> The use case for augment inside anything but on the top-level is to be
> used in combination with 'uses'.  The idea is that you can do 'uses
> foo', and then in a following augment add new nodes to the foo
> grouping:
> 
>   grouping server {
>     leaf name { type string; }
>     container address {
>       leaf ip { type inet:ip-address; }
>     }
>   }
> 
>   container foo {
>     uses server;
>     augment address {
>       leaf port { type inet:port-number; } 
>     }
>   }      
> 
> Or the same thing as a reusable grouping:
> 
>   grouping server-with-port {
>     uses server;
>     augment address {
>       leaf port { type inet:port-number; } 
>     }
>   }      
>     
> This way extensions to groupings ("complex types":) can be defined.
> 
>> That means while you are defining extra data to attach to /acme:foo
>> you also define some extra data for /a:bar/b:baz?
> 
> Yes.
> 
>> I have only seen augment examples that appear at the top-level.
>> Are there real examples of data models that actually need to
>> nest the augment-stmt anywhere and everywhere in the data model,
>> even inside the 'input' clause for an RPC method definition?
>>
>> What are the requirements for WG or vendor data model augmentation exactly?
> 
> I'm not sure I understand this question either.
> 
> 
> /martin
> 
> 
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-- 
Balazs Lengyel                       Ericsson Hungary Ltd.
TSP System Manager
ECN: 831 7320                        Fax: [phone]
Tel: [phone]     email: [e-mail]


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