Here is the guidance I have been using in the IEEE 802 YANG coordination group.
It may not be perfect, but it makes a distinction between model and module in
what I feel is consistent.
Research based on IETF documents…
• YANG Data Model
* Not explicitly defined. Data model is defined in the terminology section
of IETF RFC 7950 as: “data model: A data model describes how data is
represented and accessed.”
• YANG Module
* In IETF RFC 7950:
* Section 3:
* module: A YANG module defines hierarchies of schema nodes. With its
definitions and the definitions it imports or includes from elsewhere, a module
is self-contained and “compilable”.
* Section 4.1:
* “YANG structures data models into modules and submodules.”
* Section 4.2.1:
* “YANG data models are defined in modules. A module contains a
collection of related definitions.”
* Section 5.2: “YANG modules and submodules are typically stored in
files, one “module” or “submodule” statement per file.”
IEEE 802 YANG coordination group definitions:
* YANG model
* One or more YANG modules used to configure and monitor the managed
element or system.
* YANG module
* The description of the data model used to configure and monitor the
managed element or system. A YANG module defines a hierarchy of nodes that can
be used for NETCONF-based (see IETF RFC 7803) and RESTCONF-based (see IETF RFC
8040) operations.
* Schema tree
* The definition hierarchy specified within a module. [IETF RFC 7950]
* Schema
* A collection of schema trees with a common root. [IETF RFC 8528]
Hope this helps.
-scott.
From: IGNACIO DOMINGUEZ MARTINEZ-CASANUEVA
<[email protected]>
Sent: Tuesday, September 24, 2024 4:59 AM
To: [email protected]
Subject: [netmod] YANG module vs YANG data model
Dear NETMOD WG,
Since I started working with YANG, I have felt the impression that we tend to
use the terms “module” and “model” indistinctly, leading to misunderstandings.
According to RFC7950:
“a data model describes how data is represented and accessed.”
And later we can find:
“YANG structures data models into modules and submodules.”
And:
“YANG data models are defined in modules. A module contains a
collection of related definitions.”
The identification and versioning of YANG modules and submodules is clear, and
in fact, keeps evolving as we have seen in the YANG Semantic
Versioning<https://datatracker.ietf.org/doc/draft-ietf-netmod-yang-semver/>
discussions. However, when it comes to YANG data models, to the best of my
knowledge, there are no means for identifying them.
In my opinion, this is a limitation that is hindering the cataloguing and
access to YANG data. From the standpoint of a data consumer, what you care
about is the data model, that is, the compiled hierarchy or collection of
imported, deviation, and augmentation modules. Let’s put an example with two
different data models:
1. Module A (name: module-A) --> augmented by Module B (name:module-B)
2. Module A (name: module-A) --> augmented by Module C (name:module-C)
How do we refer to the first data model? Should we name it “module-A”, like the
parent or root module? Please, also note here that concepts like “parent
module” or “root module” have not been formally defined in the scope of YANG
data modelling.
How about the second data model in the example? We cannot name it “module-A” as
we would have a naming conflict with the first data model.
I have seen other activities within the IETF that have come across this issue.
For instance, An Architecture for YANG-Push to Message Broker
Integration<https://datatracker.ietf.org/doc/draft-ietf-nmop-yang-message-broker-integration/00/>
with the implementation of the YANG Schema Registry. In this case, the YANG
data models (not the modules), and therefore, the YANG schemas, need to be
uniquely identified in the registry. However, the algorithm used for generating
the schema IDs is still unclear.
I think the YANG
Packages<https://datatracker.ietf.org/doc/draft-ietf-netmod-yang-packages/>
draft aimed at solving this, though I’m missing why the document was abandoned.
I would kindly appreciate I someone could shed some light.
Many thanks!
Best regards,
Nacho.
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