Re: [netmod] Module tags

[Kent Watsen <[e-mail]>]

As for a concrete use-case, would something like this be helpful
for a server to indicate which datastores a module is supported in?

I'm thinking specifically about the revised-datastores draft where
we've discussed that a module might exist in just oper-state,
oper-state + ephemeral, oper-state + ephemeral + running, etc.


Kent // as a contributor




Hi tags draft authors,

On 09/02/2017 12:28, Lou Berger wrote:
>
> I'm personally more excited by the use of tags as additional module 
> meta-data accessible via yang library. But also see no reason to 
> preclude this possible  (even if unlikely) usage.

When the idea of tags was presented as IETF, I had assumed that tags 
would be versioned/managed entirely independently from the YANG modules 
that the tags apply to.

For a while, there was a desire to organize YANG modules by their 
hierarchical path location in the schema tree.  My concern with this 
approach, is that there needs to be sufficient foresight to get that 
structure right now, because it will be very painful to change it in 
future.  Unfortunately things have a habit of evolving over time, and 
hence choosing the right structure now such that is still the right 
structure in 25 years seems somewhat unlikely.

I was thinking that tags offers a better solution to this problem, that 
allows the structure to be a bit more dynamic, evolving over time.  I.e. 
YANG modules for features can sit at (or near to) the top level of the 
schema tree, and tags can then be used to group those modules into 
sensible organizations that can evolve, so that when clients are trying 
to sort through all the different YANG models that are available, they 
have more hope than looking at a flat list.

In this scenario, I think that it is better if the YANG module 
definitions themselves don't specify the tags because then 
adding/removing/changing them is going to be a pain.  If this tag 
information was managed separately (e.g. in something like YANG catalog) 
then it seems easier for the tags to evolve over time.

But I also had not really realized that the tags information would 
necessarily reach down to the devices.  I.e. I hadn't envisaged Chris's 
example of querying the hello-time via an IGP package tag. Instead, I 
had thought of tags making a YANG catalog website more useful.  E.g. 
when browsing for YANG modules, be able to restrict the query to just 
the modules that are tagged as "standard" + "IGP", etc.

So, I think that this draft may benefit with a bit more description of 
the envisaged use cases, and also about how tags are envisaged to evolve 
once they have been defined.

Thanks,
Rob

>
> Lou
>
>
>> Thanks,
>> Chris.
>
>
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