Re: [netmod] WGLC on draft-ietf-netmod-node-tags-06

[Qin Wu <[e-mail]>]

Balazs:
Thank for clarification, I feel whether this extension statement is backwards-compatible changes are generic issue that are applicable to all YANG extension related documents and standards.
Maybe it is worth writing a separate document to talk about backward compatibility of those yang extensions. 
For yang extension introduced in this draft is just for data classification, the impact of adding or removing data node tag is just to influence the precision or granularity of data classification.
Therefore I think changing these extension is just backwards-compatible change.

-Qin
-----邮件原件-----
发件人: Balázs Lengyel [mailto:balazs.lengyel=[e-mail]] 
发送时间: 2022年4月19日 16:04
收件人: Qin Wu <[e-mail]>; Jürgen Schönwälder <[e-mail]>
抄送: [e-mail]
主题: RE: [netmod] WGLC on draft-ietf-netmod-node-tags-06

>- for each extension statement the following should be described
>   + Changing this extension statement is a backwards-compatible change  
>yes/no/editorial-only
[Qin Wu] Can you provide an example for this issue or reference document, I can not find any guideline in RFC7950.

BALAZS: It is the first question you get from a customer at any model update/upgrade: are the changes backwards compatible?
The modeler and the customer needs to understand whether a change in the extension statements is backwards compatible or not. 
The new YANG versioning drafts also require this knowledge.
E.g. 
Removing the nacm:default-deny-all extension from a leaf is backwards compatible as all earlier operations will still work Adding the nacm:default-deny-all extension to a leaf is not  backwards compatible as writing to the leaf might not work anymore.

Regards Balazs