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

[Jürgen Schönwälder <[e-mail]>]

On Mon, Apr 11, 2022 at 11:52:10AM +0000, Qin Wu wrote:
> >I have not read the document in detail yet but I find the notion of data objects and subobjects confusing. I also do not know what "massive" data object collections are or why both objects and subobjects can be modeled as YANG data nodes, or what the 
> >purpose of this statement is. 
> 
> [Qin Wu] massive data collection might consume large amount of network bandwidth resource and computation resource. the data node tag help us capture characteristics data (e.g., KPI data) and greatly reduce the data to exported to the collectors.
> Take example-module-A as an example:
>    module example-module-A {
>      //...
>      container top {
>        list X {
>          leaf foo {
>          }
>          leaf bar {
>          }
>        }
>      }
>      // ...
>    }
> The top level node will be seen as data object while leaf foo and leaf bar will be seen as subobject, the top level node will be tagged with Object tag, the child node will be tagged with other tag such as metric tag or metric type tags.
> Note that the notion of data objects and subobjects is only used in the usage example in section 3. Do you think it is confusing to introduce new terminologies, if yes, I will see how to fix this.

I strongly disagree with introducing new terminology. The notion of a
data object or a subobject does not exist in YANG. All the YANG model
does is to associate tags with yang-node-identifiers. That's it and I
think the document should restrict itself to explain that.

My comment was actually more about words like "massive" being a purely
subjective term. Marketing people may use them but in technical
writing or even scientific writing, they have no real meaning. If you
are worried about scalability (and I would), then the question to ask
may be whether a single flat list is scalable to large numbers of
tags, i.e., how many queries do I need to find all relevant tags and
how do the queries scale.
 
> >When I look at ietf-data-object-tags (likely also a misnomer), then what I see is a list associating tags to anything identifiable by a nacm:node-instance-identifier. It feels like this document has a lot of hot air around something that is at the end rather basic.
> 
> [Qin Wu] Please note that RFC9196 also defines node-selector as node-instance-identifier. See the definition of node-instance-identifier in RFC8341
> "
>      typedef node-instance-identifier {
>        type yang:xpath1.0;
>        description
>          "Path expression used to represent a special
>           data node, action, or notification instance-identifier
>           string.
> 
>           A node-instance-identifier value is an
>           unrestricted YANG instance-identifier expression.
>           All the same rules as an instance-identifier apply,
>           except that ***predicates**** for keys are optional.
>           If a key
>           predicate is missing, then the node-instance-identifier
>           represents all possible server instances for that key. "
> It can represent one specific node instance,e.g.,
>      /* instance-identifier for a list entry */
>      /ex:system/ex:user[ex:name='fred']
> or all possible node instance if the predicates is not specified, e.g.,
>      /* instance-identifier for all list entry/
>         /ex:system/ex:user
> For the latter case, it can also be seen as at node level or schema node level if my understanding is correct.

I can't tell right now whether RFC 9196 makes proper use of
nacm:node-instance-identifier. Anyway, this is important material
to explain, not the data objects massive kind of marketing text.

/js

-- 
Jürgen Schönwälder              Jacobs University Bremen gGmbH
Phone: [phone]         Campus Ring 1 | 28759 Bremen | Germany
Fax:   [phone]         <https://www.jacobs-university.de/>