Re: [netmod] Backward Compatibility Question

Hi,

It would change the schema node for an object if it was wrapped it in a
choice.
This affects augment and deviation statements that reference the old schema
node.
The 'uses' node is a special case since it never appears in a schema node
identifier.

Andy

On Mon, Oct 2, 2017 at 9:31 AM, Kent Watsen <kwatsen@juniper.net> wrote:

> Hi Joey,
>
> Your proposal looks fine to me, since it doesn't change the semantics of
> the data model.  Note that https://tools.ietf.org/html/rfc7950#section-11
> says:
>
>    o  Any set of data definition nodes may be replaced with another set
>       of syntactically and semantically equivalent nodes.  For example,
>       a set of leafs may be replaced by a "uses" statement of a grouping
>       with the same leafs.
>
> Kent
>
> --
>
> Hello,
>
> Does anyone have thoughts on this?
>
> Regards,
> Joey
>
> -----Original Message-----
> From: JOEY BOYD
> Sent: Wednesday, September 27, 2017 9:06 AM
> To: 'netmod@ietf.org'
> Subject: Backward Compatibility Question
>
> Hi all,
>
> Suppose I had a published YANG model with the following leaf.
>
>
>   leaf thing1 {
>     type uint8;
>     description
>       "Thing 1.";
>   }
>
> Later, I realize that I wish I had modeled this in a choice as I now have
> a mutually exclusive option to 'thing1' which I want to add to the model.
>
>   leaf thing2 {
>     type empty;
>     description
>       "Thing 2.";
>   }
>
> This is a very simplified example but should be sufficient to demonstrate
> the problem.
>
> If I look at the XML representation of 'thing1', it looks like this.
>
> <thing1>123</thing1>
>
> If I were to move 'thing1' into a choice with a single case, it would look
> like this.
>
> choice things {
>   case thing1 {
>     leaf thing1 {
>       type uint8;
>       description
>         "Thing 1.";
>     }
>   }
> }
>
> Looking to the XML representation, it looks the same as before.
>
> <thing1>123</thing1>
>
> To me, this means that taking a single node or set of nodes and moving
> them under a case within a new choice statement is a backward compatible
> change. This assumes, of course, any mandatory or default behavior is
> preserved. I now can add 'thing2' to the existing model as an option to
> 'thing1'.
>
> choice things {
>   case thing1 {
>     leaf thing1 {
>       type uint8;
>       description
>         "Thing 1.";
>     }
>   }
>   case thing2 {
>     leaf thing2 {
>       type empty;
>       description
>         "Thing 2.";
>     }
>   }
> }
>
> Do you agree with this analysis or am I missing something?
>
> Best regards,
> Joey
>
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