Self Describing Data Object Tags
draft-ietf-netmod-node-tags-03

Document Type Active Internet-Draft (netmod WG)
Authors Qin Wu  , Benoît Claise  , Peng Liu  , Zongpeng Du  , Mohamed Boucadair 
Last updated 2021-05-13
Replaces draft-tao-netmod-yang-node-tags
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NETMOD Working Group                                               Q. Wu
Internet-Draft                                                 B. Claise
Updates: 8407 (if approved)                                       Huawei
Intended status: Standards Track                                  P. Liu
Expires: November 14, 2021                                         Z. Du
                                                            China Mobile
                                                            M. Boucadair
                                                                  Orange
                                                            May 13, 2021

                    Self Describing Data Object Tags
                     draft-ietf-netmod-node-tags-03

Abstract

   This document defines a method to tag data objects associated with
   operation and management data in YANG modules.  This YANG data object
   tagging method can be used to classify data objects from different
   YANG modules and identify their characteristics data.  It can also
   provide input, instruction, indication to selection filter, and
   filter queries of operational state on a server during a "pub/sub"
   service for YANG datastore updates.  When the subscriptions of a
   particular subscriber to be fetched is very large, the amount of data
   to be streamed out to the destination can be reduced and only
   targeted to the characteristics data.  These data object tags may be
   registered as well as assigned during the module definition, assigned
   by implementations, or dynamically defined and set by users.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at https://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on November 14, 2021.

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Copyright Notice

   Copyright (c) 2021 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (https://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   4
     2.1.  Requirements Notation . . . . . . . . . . . . . . . . . .   4
     2.2.  Glossary  . . . . . . . . . . . . . . . . . . . . . . . .   4
   3.  Self Describing Data Object Tags: Massive Data Object
       Collection Use Case . . . . . . . . . . . . . . . . . . . . .   4
   4.  Data Object Tag Values  . . . . . . . . . . . . . . . . . . .   6
     4.1.  IETF Tags Prefix  . . . . . . . . . . . . . . . . . . . .   7
     4.2.  Vendor Tags Prefix  . . . . . . . . . . . . . . . . . . .   7
     4.3.  User Tags Prefix  . . . . . . . . . . . . . . . . . . . .   7
     4.4.  Reserved Tags Prefix  . . . . . . . . . . . . . . . . . .   7
   5.  Data Object Tag Management  . . . . . . . . . . . . . . . . .   7
     5.1.  Module Design Tagging . . . . . . . . . . . . . . . . . .   8
     5.2.  Implementation Tagging  . . . . . . . . . . . . . . . . .   9
     5.3.  User Tagging  . . . . . . . . . . . . . . . . . . . . . .   9
   6.  Data Object Tags Module Structure . . . . . . . . . . . . . .   9
     6.1.  Data Object Tags Module Tree  . . . . . . . . . . . . . .   9
   7.  YANG Module . . . . . . . . . . . . . . . . . . . . . . . . .   9
   8.  Guidelines to Model Writers . . . . . . . . . . . . . . . . .  12
     8.1.  Define Standard Tags  . . . . . . . . . . . . . . . . . .  12
   9.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  13
     9.1.  YANG Data Object Tag Prefixes Registry  . . . . . . . . .  13
     9.2.  IETF YANG Data Object Tags Registry . . . . . . . . . . .  14
     9.3.  Updates to the IETF XML Registry  . . . . . . . . . . . .  16
     9.4.  Updates to the YANG Module Names Registry . . . . . . . .  16
   10. Security Considerations . . . . . . . . . . . . . . . . . . .  16
   11. Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  17
   12. Contributors  . . . . . . . . . . . . . . . . . . . . . . . .  17
   13. References  . . . . . . . . . . . . . . . . . . . . . . . . .  17
     13.1.  Normative References . . . . . . . . . . . . . . . . . .  17
     13.2.  Informative References . . . . . . . . . . . . . . . . .  19

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   Appendix A.  NETCONF Example  . . . . . . . . . . . . . . . . . .  19
   Appendix B.  Non-NMDA State Module  . . . . . . . . . . . . . . .  20
   Appendix C.  Targeted data object collection example  . . . . . .  23
   Appendix D.  Changes between Revisions  . . . . . . . . . . . . .  26
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  27

1.  Introduction

   As described in [RFC8819], the use of tags for classification and
   organization is fairly ubiquitous not only within IETF protocols, but
   in the Internet itself (e.g., "#hashtags").  As a reminder, a module
   tag defined in [I.D-ietf-netmod-module-tags] is a string associated
   only with a module name at the module level.

   At the time of writing this document (2020), there are many data
   models that have been specified or are being specified by various
   SDOs and the Open Source community.  These models cover many of the
   networking protocols and techniques.  However, data objects defined
   by these technology-specific data models might represent a portion of
   fault, configuration, accounting, performance, and security
   management categories information at different locations in various
   different ways.  Let alone the lack consistent classification
   criteria and representation for a specific service, feature, or data
   source.

   This document defines self-describing data object tags and associates
   them with data objects within a YANG module, which:

   o  Provide dictionary meaning for specific targeted data objects.

   o  Indicate relationship between data objects within the same YANG
      module or from different YANG modules.

   o  Identify key performance metric data objects and the absolute
      XPath expression identifying the element path to the node.

   The self describing data object tags can be used by the NETCONF/
   RESTCONF client to classify data objects from different YANG modules
   and identify characteristics data.  In addition, it can provide
   input, instruction, indication to selection filter and filter queries
   of configuration or operational state on a server based on these data
   object tags, e.g., return specific object type of operational state
   related to system-management.  NETCONF clients can discover data
   objects with self describing data object tags supported by a NETCONF
   server by means of <get-schema> operation.  The self describing data
   object tag capability can also be advertised using the capability
   notification model [I-D.netconf-notification-capabilities] by the
   NETCONF server or some place where offline document are kept.  These

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   data object tags may be registered or assigned during the module
   definition, assigned by implementations, or dynamically defined and
   set by users.

   This document defines a YANG module [RFC7950] which augments the
   module tag model and provides a list of data object entries to allow
   for adding or removing of self describing tags as well as viewing the
   set of self describing tags associated with specific data objects
   within YANG modules.

   This document defines an extension statement to be used to indicate
   self describing tags that should be added by the module
   implementation automatically (i.e., outside of configuration).

   This document also defines an IANA registry for tag prefixes as well
   as a set of globally assigned tags (Section 9).

   Section 8 provides guidelines for authors of YANG data models.

   The YANG data model in this document conforms to the Network
   Management Datastore Architecture defined in [RFC8342].

   The meaning of the symbols can be found in [RFC8340].

2.  Terminology

2.1.  Requirements Notation

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in BCP
   14 [RFC2119][RFC8174] when, and only when, they appear in all
   capitals, as shown here.

2.2.  Glossary

   OPM   Object Property Metric

3.  Self Describing Data Object Tags: Massive Data Object Collection Use
    Case

   Among data object tags, the 'opm' (object, property, metric) tags can
   be used to tackle massive data objects collection and only capture
   YANG data objects associated with performance metrics data modelled
   with YANG (Figure 1).

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                     /----\
                    /Object\
                    | Tag  |
                     \- +-/
              +---------V--------+    have
              | YANG Data Node   <----------------+
              | /Data Object 1   |                |
              +--^-------------^-+                |
                 |have         |have              |
                 |             |                  |
   +-------------+-----+     +-+-------------+  +-+-------------+
   |   YANG Data Node  |     | YANG Data Node|  | YANG Data Node|
   |  /Data Object 2   |     | /Data Object 3|  | /Data Object 4|
   +---^---------------+     +-^-------------+  +-^-------------+
       |                       |                  |
       |                     /-+-\              /-+-\
     /-+--\                /Metric \          /Metric \
    Property               |  Tag  |          |  Tag  |
    \ Tag  /                 \-^-/              \-^-/
     \----/                    |                  |
                               |      /----\      |
                               |     /Metric\     |
                               +----|  Group +----|
                                     \  Tag /
                                      \- --/

        Figure 1: The Relation between Object, Property and Metric

   In Figure 1, data objects can contain other data objects called
   subobjects.  Both object and subobjects can be modeled as YANG data
   nodes [RFC7950].  Data objects that contain other data objects can be
   one of 'container', 'leaf-list', and 'list' and are tagged with
   object tag.  A subobject tagged with the property tag is a 'leaf'
   node.  Subobjects tagged with the metric tag can be one of
   'container', 'leaf-list', 'list', or 'leaf' data node.

   A data object contains one single object tag, one single property
   tag, or one single metric tag.  A data object tagged with metric tag
   also can have one or multiple Metric Type tags and/or one single
   multi-source tag.

   The use of 'opm' tags is meant to help filter discrete categories of
   YANG data objects scattered across the same or different YANG modules
   supported by a device and capture all network performance data or all
   property data in the single view of the data.  In Figure 2, 'tunnel-
   svc' data object is a container node defined in the 'tunnel-pm'
   module and can be seen as the root object for property tagged
   subobjects (e.g., 'tunnel-svc'/'create-time') and metric tagged

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   subobjects (e.g., 'tunnel-svc'/'avg-latency').  The 'name', 'create-
   time', and 'modified-time' are property tagged subobjects under
   'tunnel-svc' container.  The 'avg-latency' and 'packet-loss' metrics
   are tagged subobjects under 'tunnel-svc' container node.  Consider
   'tunnel-svc' data object and tunnel-svc/name data object as an
   example, 'tunnel-svc' data object has one single object tag (i.e.,
   'ietf:object') while tunnel-svc/name data object has one property
   subobject tag (i.e., 'ietf:property').  In addition, not all metric
   subobjects need to be tagged, e.g., only specific category such as
   loss-related metric subobjects need to be tagged with metric-type tag
   which can further reduce amount data to be fetched.

 +------------------------+--------------------------------------------+
 |      Data              |  Object    Property     Metric      Module |
 |      Object            |   Tag        Tag         Tag         Name  |
 +------------------------+--------------------------------------------+
 |                        |  ietf:                                     |
 |tunnel-svc              |  object                           tunnel-pm|
 |                        |            ietf:                           |
 |tunnel-svc/name         |            property               tunnel-pm|
 |                        |            ietf:                           |
 |tunnel-svc/create-time  |            property               tunnel-pm|
 |                        |            ietf:                           |
 |tunnel-svc/modified-time|            property               tunnel-pm|
 |                        |                                            |
 |tunnel-svc/avg-latency  |                        ietf:      tunnel-pm|
 |                        |                        metric              |
 |tunnel-svc/packet-loss  |                        ietf:      tunnel-pm|
 |                        |                        metric              |
 |tunnel-svc/min-latency  |                        ietf:      tunnel-pm|
 |                        |                        metric              |
 |tunnel-svc/ max-latency |                        ietf:      tunnel-pm|
 |                        |                        metric              |
 +------------------------+--------------------------------------------+

           Figure 2: Example of OPM Tags Used in the YANG Module

   If data objects in YANG modules are suitably tagged and learnt by the
   client from a live server, the client can retrieve paths to all
   targeted data objects and then use an XPath query defined
   [RFC8639][RFC8641] to list all tagged data objects which reflect
   network characteristics.

4.  Data Object Tag Values

   All data object tags SHOULD begin with a prefix indicating who owns
   their definition.  To that aim, an IANA registry (Section 9.1) is

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   used to support registering data object tag prefixes.  Three prefixes
   are defined in the following subsections.

   No further structure is imposed by this specification on the value
   following the registered prefix other than the value can contain any
   YANG type 'string' characters except carriage-returns, newlines, and
   tabs.  Therefore, designers, implementers, and users are free to add
   or not any structure they may require to their own tag values.

4.1.  IETF Tags Prefix

   An IETF tag is a data object tag that has the prefix "ietf:".

   All IETF data object tags are registered with IANA in a registry
   defined Section 9.2.

4.2.  Vendor Tags Prefix

   A vendor tag is a tag that has the prefix "vendor:".

   These tags are defined by the vendor that implements the module, and
   are not registered.  However, it is RECOMMENDED that the vendor
   includes extra identification in the tag to avoid collisions such as
   using the enterprise or organization name following the "vendor:"
   prefix (e.g., vendor:vendor-defined-classifier).

4.3.  User Tags Prefix

   A user tag is any tag that has the prefix "user:".

   These tags are defined by the user/administrator and are not meant to
   be registered.  Users are not required to use the "user:" prefix;
   however, doing so is RECOMMENDED as it helps avoid prefix collisions.

4.4.  Reserved Tags Prefix

   Any tag not starting with the prefix "ietf:", "vendor:" or "user:" is
   reserved for future use.  These tag values are not invalid, but
   simply reserved in the context of specifications (e.g., RFCs).

5.  Data Object Tag Management

   Tags may be associated with a data object within a YANG module in a
   number of ways.  Typically, tags may be defined and associated at the
   module design time, at implementation time without the need of live
   server, or via user administrative control.  As the main consumer of
   data object tags are users, users may also remove any tag from a live

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   server, no matter how the tag became associated with a data object
   within a YANG module.

5.1.  Module Design Tagging

   A data object definition MAY indicate a set of data object tags to be
   added by a module's implementer.  These design time tags are
   indicated using a set of extension statements which include:

   opm-tag extension statement:  Classifies management and operation
      data into object, property subobject, and metric subobject
      categories.  Both object and subobjects can be modeled as YANG
      data nodes [RFC7950].  Data objects that contain other data
      objects can be one of 'container', 'leaf-list', and 'list' and are
      tagged with object tag.  A subobject tagged with the property tag
      is a 'leaf' node.  Subobjects tagged with the metric tag can be
      one of 'container', 'leaf-list', 'list', or 'leaf' data node.  A
      data object contains one single object tag, one single property
      tag, or one single metric tag.  A data object tagged with metric
      tag also can have one or multiple Metric type tag and/or one
      single multi-source tag.  See the examples depicted in Figure 2
      and Figure 3.

   metric-type extension statement:  Provides metric data objects
      classification (e.g., loss, jitter, delay, counter, gauge,
      histogram, summary, unknown) within the YANG module.

   multi-source-tag extension statement:  Identifies multi-source
      aggregation type (e.g., aggregated, non-aggregated) related to
      metric subobject. 'aggregated' multi-source aggregation type
      allows a large number of measurements on metric subobjects from
      different sources of the same type (e.g., line card, each
      subinterface of aggregated Ethernet interface) being combined into
      aggregated statistics and report as one metric subobject.  'non-
      aggregated' multi-source aggregation type allows measurement from
      each source of the same type (e.g., line card, each subinterface
      of aggregated Ethernet interface) be reported separately.

   Among these extension statements, the metric-type and multi-source-
   tag extension statements are context information that can be used to
   correlate data object from the different modules.

   If the data node is defined in an IETF standards track document, the
   data object tags MUST be IETF Tags (Section 4.1).  Thus, new data
   object can drive the addition of new IETF tags to the IANA registry
   defined in Section 9, and the IANA registry can serve as a check
   against duplication.

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5.2.  Implementation Tagging

   An implementation MAY include additional tags associated with data
   object within a YANG module.  These tags SHOULD be IETF Tags (i.e.,
   registered) or vendor specific tags.

5.3.  User Tagging

   Data object tags of any kind, with or without a prefix, can be
   assigned and removed by the user from a live server using normal
   configuration mechanisms.  In order to remove a data object tag from
   the operational datastore, the user adds a matching "masked-tag"
   entry for a given data object within the 'ietf-data-object-tags'
   module.

6.  Data Object Tags Module Structure

6.1.  Data Object Tags Module Tree

   The tree associated with the "ietf-data-object-tags" module is as
   follows:

   module: ietf-data-object-tags
     augment /tags:module-tags/tags:module:
       +--rw data-object-tags
          +--rw data-object* [object-name]
             +--rw object-name    nacm:node-instance-identifier
             +--rw tag*           tags:tag
             +--rw masked-tag*    tags:tag

7.  YANG Module

<CODE BEGINS> file "ietf-data-object-tags@2021-05-03.yang"
module ietf-data-object-tags {
  yang-version 1.1;
  namespace "urn:ietf:params:xml:ns:yang:ietf-data-object-tags";
  prefix ntags;

  import ietf-netconf-acm {
    prefix nacm;
  }
  import ietf-module-tags {
    prefix tags;
  }

  organization
    "IETF NetMod Working Group (NetMod)";
  contact

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    "WG Web:  <https://tools.ietf.org/wg/netmod/>
     WG List: <mailto:netmod@ietf.org>
     Editor:  Qin Wu <mailto:bill.wu@huawei.com>
     Editor:  Benoit Claise <mailto:bclaise@cisco.com>
     Editor:  Peng Liu <mailto:liupengyjy@chinamobile.com>
     Editor:  Zongpeng Du <mailto:duzongpeng@chinamobile.com>
     Editor:  Mohamed Boucadair <mailto:mohamed.boucadair@orange.com>";
  description
    "This module describes a mechanism associating self-describing
     tags with YANG data object within YANG modules. Tags may be IANA
     assigned or privately defined.

     Copyright (c) 2021 IETF Trust and the persons identified as
     authors of the code. All rights reserved.

     Redistribution and use in source and binary forms, with or
     without modification, is permitted pursuant to, and subject to
     the license terms contained in, the Simplified BSD License set
     forth in Section 4.c of the IETF Trust's Legal Provisions
     Relating to IETF Documents
     (https://trustee.ietf.org/license-info).

     This version of this YANG module is part of RFC XXXX
     (https://tools.ietf.org/html/rfcXXXX); see the RFC itself for
     full legal notices.";

  revision 2021-05-03 {
    description
      "Initial revision.";
    reference
      "RFC XXXX: Self Describing Data Object Tags";
  }

  extension opm-tag {
    argument tag;
    description
      "The argument 'tag' is of type 'tag'. This extension statement
       is used by module authors to indicate the opm tags that should
       be added automatically by the system. Opm Tag is used to
       classify operation and management data object into object,
       property, and metric three categories. Data Object can contain
       other data objects called subobjects. Both object and subobjects
       can be modeled as data nodes. The Data Object tagged with object
       tag can be one of container, leaf-list and list. Data Object
       tagged with the Property tag is a leaf node. Data Object tagged with
       the Metric tag can be one of container, leaf-list, list, leaf.
       Data objects tagged with either property tag or metric tag are
       subobjects belonging to specific root data object.  Data Object

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       contains One object tag or one property tag, or one metric tag. As
       such the origin of the value for the pre-defined tags should be set
       to 'system'.";
  }

  extension metric-type {
    argument tag;
    description
      "The argument 'tag' is of type 'tag'. The metric type can be
       used to provide metric data object classification
       (e.g., loss, jitter, packet loss,counter, gauge, histogram,
       summary, unknown) within the YANG module.";
  }

  extension multi-source-tag {
    argument tag;
    description
      "The argument 'tag' is of type 'tag'. The multi-source-tag can be
       used to identify  multi-source aggregation type (e.g., aggregated,
       non-aggregated) related to metric subobject.

      'aggregated' multi-source aggregation type allows a large number of
      measurements on metric subobjects from different sources of the same
      type (e.g., line card, each subinterface of aggregated Ethernet interface)
      being combined into aggregated statistics and report as one metric subobject
      value. 'non-aggregated' multi-source aggregation type allows measurement from
      each source of the same type (e.g., line card, each subinterface of aggregated
      Ethernet interface) be reported separately.";
   }

  augment "/tags:module-tags/tags:module" {
    description
      "Augment the Module Tags module with data object tag attributes";
    container data-object-tags {
      description
        "Contains the list of data objects and their associated data object tags";
      list data-object {
        key "object-name";
        description
          "A list of data objects and their associated data object tags";
        leaf object-name {
          type nacm:node-instance-identifier;
          mandatory true;
          description
            "The YANG data object name.";
        }
        leaf-list tag {
          type tags:tag;

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          description
            "Tags associated with the data object within the YANG module. See
             the IANA 'YANG Data Object Tag Prefixes' registry for reserved
             prefixes and the IANA 'IETF YANG Data Object Tags' registry for
             IETF tags.

             The 'operational' state view of this list is
             constructed using the following steps:

             1) System tags (i.e., tags of 'system' origin) are added.
             2) User configured tags (i.e., tags of 'intended' origin)
             are added.
             3) Any tag that is equal to a masked-tag is removed.";
        }
        leaf-list masked-tag {
          type tags:tag;
          description
            "The list of tags that should not be associated with the data
             object within the YANG module. The user can remove (mask) tags from the
             operational state datastore by adding them to
             this list. It is not an error to add tags to this list
             that are not associated with the data object within YANG module,
             but they have no operational effect.";
        }
      }
    }
  }
}
<CODE ENDS>

8.  Guidelines to Model Writers

   This section updates [RFC8407].

8.1.  Define Standard Tags

   A module MAY indicate, using data object tag extension statements, a
   set of data object tags that are to be automatically associated with
   data object within the module (i.e., not added through
   configuration).

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    module example-module-A {
           //...
           import ietf-data-node-tags { prefix ntags; }
           container top {
             ntags:opm-tag "ietf:object";
            list X {
              leaf foo {
              ntags:opm-tag "ietf:property";
               }
             }
           container Y {
             leaf bar {
             ntags:opm-tag "ietf:metric";
             }
         }
       }
     // ...
    }

                     Figure 3: Data object tag example

   The module writer can use existing standard data object tags, or use
   new data object tags defined in the data object definition, as
   appropriate.  For IETF standardized modules, new data object tags
   MUST be assigned in the IANA registry defined below, see
   Section Section 9.2.

9.  IANA Considerations

9.1.  YANG Data Object Tag Prefixes Registry

   This document requests IANA to create a new registry entitled "YANG
   Data Object Tag Prefixes" grouped under a new "Protocol" category
   named "YANG Data Object Tag Prefixes".

   This registry allocates tag prefixes.  All YANG Data Object Tags
   should begin with one of the prefixes in this registry.

   Prefix entries in this registry should be short strings consisting of
   lowercase ASCII alpha-numeric characters and a final ":" character.

   The allocation policy for this registry is Specification Required
   [RFC8126].  The Reference and Assignee values should be sufficient to
   identify and contact the organization that has been allocated the
   prefix.

   The initial values for this registry are as follows:

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   +----------+----------------------------------+-----------+----------+
   | Prefix   | Description                      | Reference | Assignee |
   +----------+----------------------------------+-----------+----------+
   | ietf:    | IETF Tags allocated in the IANA  | [This     | IETF     |
   |          | IETF YANG Data Object Tags       | document] |          |
   |          | registry                         |           |          |
   |          |                                  |           |          |
   | vendor:  | Non-registered tags allocated by | [This     | IETF     |
   |          | the module's implementer.        | document] |          |
   |          |                                  |           |          |
   | user:    | Non-registered tags allocated by | [This     | IETF     |
   |          | and for the user.                | document] |          |
   +----------+----------------------------------+-----------+----------+

   Other standards organizations (SDOs) wishing to allocate their own
   set of tags should allocate a prefix from this registry.

9.2.  IETF YANG Data Object Tags Registry

   This document requests IANA to create three new registries "IETF OPM
   Tags","IETF Metric Type Tags","IETF Multiple Source Tags" grouped
   under a new "Protocol" category.  These 3 registries should be
   included below "YANG Data Object Tag Prefixes" when listed on the
   same page.

   Three registries are used to allocate tags that have the registered
   prefix "ietf:".  New values should be well considered and not
   achievable through a combination of already existing IETF tags.

   The allocation policy for these three registries is IETF Review
   [RFC8126].

   The initial values for these three registries are as follows:

   +----------------------------+--------------------------+-----------+
   | OPM Tag                    | Description              | Reference |
   +----------------------------+--------------------------+-----------+
   |                            |                          |           |
   | ietf:object                |Represents Root object    | [This     |
   |                            |containing other data     |document]  |
   |                            |objects (e.g., interfaces)|           |
   |                            |                          |           |
   | ietf:property              |Represents  a property    | [This     |
   |                            |data object(e.g., ifindex)| document] |
   |                            |associated with a specific|           |
   |                            |root object (e.g.,        |           |
   |                            |interfaces)               |           |
   |                            |                          |           |

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   | ietf:metric                |Represent metric data     | [This     |
   |                            |object(e.g., ifstatistics)| document] |
   |                            |associated with specific  |           |
   |                            |root object(e.g.,         |           |
   |                            |interfaces)               |           |
   +----------------------------+--------------------------+-----------+
   +----------------------------+--------------------------+-----------+
   | Metric Type Tag           | Description               | Reference |
   +----------------------------+--------------------------+-----------+
   | ietf:delay                 |Represents the delay metric           |
   |                            |group to which the metric | [This     |
   |                            |data objects belong to.   | document] |
   |                            |                          |           |
   | ietf:jitter                |Represents the jitter metric [This    |
   |                            |group to which the metric |document]  |
   |                            |data objects belong to.   |           |
   |                            |                          |           |
   | ietf:loss                  |Represents the loss metric| [This     |
   |                            |group to which the metric | document] |
   |                            |data objects belong to.   |           |
   |                            |                          |           |
   | ietf:counter               |Represents any metric value           |
   |                            |associated with a metric  |           |
   |                            |data object that monotonically[This   |
   |                            |increases over time,      | document] |
   |                            |starting from zero.       |           |
   |                            |                          |           |
   | ietf:gauge                 |Represents current        |           |
   |                            |measurements associated   | [This     |
   |                            |with a metric data object |document]  |
   |                            |that may increase,        |           |
   |                            |decrease or stay constant.|           |
   |                            |                          |           |
   | ietf:histogram             |Represents the frequency of [This     |
   |                            |value observations        | document  |
   |                            |associated with a metric  |           |
   |                            |data object that falls into           |
   |                            |specific predefined range.|           |
   |                            |                          |           |
   | ietf:histogram             |Represents the metric value [This     |
   |                            |associated with a metric  | document  |
   |                            |data object that measures |           |
   |                            |distributions of discrete |           |
   |                            |events without knowing    |           |
   |                            |predefined range.         |           |
   |                            |                          |           |
   | ietf:unknown               |Represents the metric value [This     |
   |                            |associated with metric    | document  |

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   |                            |data object that can not  |           |
   |                            |determine the type of metric.         |
   +----------------------------+--------------------------+-----------+

   +----------------------------+--------------------------+-----------+
   | Multiple Source Tag        | Description              | Reference |
   +----------------------------+--------------------------+-----------+
   |ietf:agg                    |Relates to multiple sources [This     |
   |                            |aggregation type (i.e.,   | document] |
   |                            |aggregated statistics)    |           |
   |                            |                          |           |
   |ietf:non-agg                |Relates to multiple sources [This     |
   |                            |aggregation type (i.e.,   | document] |
   |                            |non-aggregated statistics)|           |
   +----------------------------+--------------------------+-----------+

   Each YANG data object can have one 'opm' tag, zero or one metric-type
   tag, zero or one multi-source tag.

9.3.  Updates to the IETF XML Registry

   This document requests IANA to register a new URI in the "IETF XML
   Registry" [RFC3688].  Following the format in [RFC3688], the
   following registration has been made:

      URI: urn:ietf:params:xml:ns:yang:ietf-data-object-tags
      Registrant Contact: The IESG.
      XML: N/A; the requested URI is an XML namespace.

9.4.  Updates to the YANG Module Names Registry

   This document requests IANA to register one YANG module in the "YANG
   Module Names" registry [RFC6020].  Following the format in [RFC6020],
   the following registration has been made:

      name: ietf-data-object-tags
      namespace: urn:ietf:params:xml:ns:yang:ietf-data-object-tags
      prefix: ntags
      reference: RFC XXXX
      maintained by IANA: N

10.  Security Considerations

   The YANG module specified in this document defines schema for data
   that is designed to be accessed via network management protocols such
   as NETCONF [RFC6241] or RESTCONF [RFC8040].  The lowest NETCONF layer
   is the secure transport layer, and the mandatory-to-implement secure
   transport is Secure Shell (SSH) [RFC6242].  The lowest RESTCONF layer

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   is HTTPS, and the mandatory-to-implement secure transport is TLS
   [RFC8446].

   The Network Configuration Access Control Model (NACM) [RFC8341]
   provides the means to restrict access for particular NETCONF or
   RESTCONF users to a preconfigured subset of all available NETCONF or
   RESTCONF protocol operations and content.

   This document adds the ability to associate data object tag meta-data
   with data object within the YANG modules.  This document does not
   define any actions based on these associations, and none are yet
   defined, and therefore it does not by itself introduce any new
   security considerations.

   Users of the data object tag meta-data may define various actions to
   be taken based on the data object tag meta-data.  These actions and
   their definitions are outside the scope of this document.  Users will
   need to consider the security implications of any actions they choose
   to define.

11.  Acknowledgements

   The authors would like to thank Ran Tao for his major contributions
   to the initial modeling and use cases.  The authors would also like
   to acknowledge the comments and suggestions received from Juergen
   Schoenwaelder, Andy Bierman, Lou Berger,Jaehoon Paul Jeong, Wei Wang,
   Yuan Zhang, Ander Liu, Peng Liu, YingZhen Qu, Boyuan Yan.

12.  Contributors

         Liang Geng
         China Mobile
         32 Xuanwumen West St, Xicheng District
         Beijing  10053

         Email: gengliang@chinamobile.com

13.  References

13.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/info/rfc2119>.

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   [RFC3688]  Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,
              DOI 10.17487/RFC3688, January 2004,
              <https://www.rfc-editor.org/info/rfc3688>.

   [RFC6020]  Bjorklund, M., Ed., "YANG - A Data Modeling Language for
              the Network Configuration Protocol (NETCONF)", RFC 6020,
              DOI 10.17487/RFC6020, October 2010,
              <https://www.rfc-editor.org/info/rfc6020>.

   [RFC7950]  Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language",
              RFC 7950, DOI 10.17487/RFC7950, August 2016,
              <https://www.rfc-editor.org/info/rfc7950>.

   [RFC8040]  Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF
              Protocol", RFC 8040, DOI 10.17487/RFC8040, January 2017,
              <https://www.rfc-editor.org/info/rfc8040>.

   [RFC8126]  Cotton, M., Leiba, B., and T. Narten, "Guidelines for
              Writing an IANA Considerations Section in RFCs", BCP 26,
              RFC 8126, DOI 10.17487/RFC8126, June 2017,
              <https://www.rfc-editor.org/info/rfc8126>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.

   [RFC8341]  Bierman, A. and M. Bjorklund, "Network Configuration
              Access Control Model", STD 91, RFC 8341,
              DOI 10.17487/RFC8341, March 2018,
              <https://www.rfc-editor.org/info/rfc8341>.

   [RFC8407]  Bierman, A., "Guidelines for Authors and Reviewers of
              Documents Containing YANG Data Models", BCP 216, RFC 8407,
              DOI 10.17487/RFC8407, October 2018,
              <https://www.rfc-editor.org/info/rfc8407>.

   [RFC8446]  Rescorla, E., "The Transport Layer Security (TLS) Protocol
              Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018,
              <https://www.rfc-editor.org/info/rfc8446>.

   [RFC8819]  Hopps, C., Berger, L., and D. Bogdanovic, "YANG Module
              Tags", RFC 8819, DOI 10.17487/RFC8819, January 2021,
              <https://www.rfc-editor.org/info/rfc8819>.

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13.2.  Informative References

   [RFC6241]  Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed.,
              and A. Bierman, Ed., "Network Configuration Protocol
              (NETCONF)", RFC 6241, DOI 10.17487/RFC6241, June 2011,
              <https://www.rfc-editor.org/info/rfc6241>.

   [RFC6242]  Wasserman, M., "Using the NETCONF Protocol over Secure
              Shell (SSH)", RFC 6242, DOI 10.17487/RFC6242, June 2011,
              <https://www.rfc-editor.org/info/rfc6242>.

   [RFC8340]  Bjorklund, M. and L. Berger, Ed., "YANG Tree Diagrams",
              BCP 215, RFC 8340, DOI 10.17487/RFC8340, March 2018,
              <https://www.rfc-editor.org/info/rfc8340>.

   [RFC8342]  Bjorklund, M., Schoenwaelder, J., Shafer, P., Watsen, K.,
              and R. Wilton, "Network Management Datastore Architecture
              (NMDA)", RFC 8342, DOI 10.17487/RFC8342, March 2018,
              <https://www.rfc-editor.org/info/rfc8342>.

   [RFC8639]  Voit, E., Clemm, A., Gonzalez Prieto, A., Nilsen-Nygaard,
              E., and A. Tripathy, "Subscription to YANG Notifications",
              RFC 8639, DOI 10.17487/RFC8639, September 2019,
              <https://www.rfc-editor.org/info/rfc8639>.

   [RFC8641]  Clemm, A. and E. Voit, "Subscription to YANG Notifications
              for Datastore Updates", RFC 8641, DOI 10.17487/RFC8641,
              September 2019, <https://www.rfc-editor.org/info/rfc8641>.

Appendix A.  NETCONF Example

   The following is a NETCONF example result from a query of the data
   object tags list.  For the sake of brevity only a few module and
   associated data object results are provided.

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<ns0:data xmlns:ns0="urn:ietf:params:xml:ns:netconf:base:1.0">
  <t:module-tags xmlns:t="urn:ietf:params:xml:ns:yang:ietf-module-tags">
    <t:module>
       <t:name>ietf-interfaces</t:name>
       <s:data-object-tags xmlns:s="urn:ietf:params:xml:ns:yang:ietf-data-object-tags">
        <s:data-object>
         <s:object-name>/if:interfaces/if:interface</s:object-name>
         <s:tag>ietf:object</s:tag>
        </s:data-object>
       <s:data-object>
        <s:object-name>/if:interfaces/if:interface/if:last-change</s:object-name>
        <s:tag>ietf:property</s:tag>
       </s:data-object>
        <s:data-object>
         <s:object-name>
          /if:interfaces/if:interface/if:statistics/if:in-errors
         </s:object-name>
         <s:tag>ietf:metric</s:tag>
        </s:data-object>
      </s:data-object-tags>
    </t:module>
    <t:module>
       <t:name>ietf-ip</t:name>
       <s:data-object-tags xmlns:s="urn:ietf:params:xml:ns:yang:ietf-data-object-tags">
       <s:data-object>
         <s:object-name>/if:interfaces/if:interface/ip:ipv4</s:object-name>
         <s:tag>ietf:object</s:tag>
       </s:data-object>
       <s:data-object>
         <s:object-name>/if:interfaces/if:interface/ip:ipv4/ip:enable</s:object-name>
         <s:tag>ietf:property</s:tag>
       </s:data-object>
        <s:data-object>
        <s:object-name>/if:interfaces/if:interface/ip:ipv4/ip:mtu</s:object-name>
        <s:tag>ietf:metric</s:tag>
       </s:data-object>
      </s:data-object-tags>
    </t:module>
  </t:module-tags>
</ns0:data>

Appendix B.  Non-NMDA State Module

   As per [RFC8407] the following is a non-NMDA module to support
   viewing the operational state for non-NMDA compliant servers.

<CODE BEGINS> file "ietf-data-object-tags-state@2021-05-03.yang"
module ietf-data-object-tags-state {

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  yang-version 1.1;
  namespace "urn:ietf:params:xml:ns:yang:ietf-data-object-tags-state";
  prefix ntags-s;

  import ietf-netconf-acm {
    prefix nacm;
  }
  import ietf-module-tags {
    prefix tags;
  }
  organization
    "IETF NetMod Working Group (NetMod)";
  contact
    "WG Web:  <https://tools.ietf.org/wg/netmod/>
     WG List: <mailto:netmod@ietf.org>
     Editor:  Qin Wu <mailto:bill.wu@huawei.com>
     Editor:  Benoit Claise <mailto:bclaise@cisco.com>
     Editor:  Peng Liu <mailto:liupengyjy@chinamobile.com>
     Editor:  Zongpeng Du <mailto:duzongpeng@chinamobile.com>
     Editor:  Mohamed Boucadair <mailto:mohamed.boucadair@orange.com>";
  description
    "This module describes a mechanism associating self-describing
     tags with YANG data object within YANG modules. Tags may be IANA
     assigned or privately defined.

     Copyright (c) 2021 IETF Trust and the persons identified as
     authors of the code. All rights reserved.

     Redistribution and use in source and binary forms, with or
     without modification, is permitted pursuant to, and subject to
     the license terms contained in, the Simplified BSD License set
     forth in Section 4.c of the IETF Trust's Legal Provisions
     Relating to IETF Documents
     (https://trustee.ietf.org/license-info).

     This version of this YANG module is part of RFC XXXX
     (https://tools.ietf.org/html/rfcXXXX); see the RFC itself for
     full legal notices.";

  revision 2021-05-03 {
    description
      "Initial revision.";
    reference
      "RFC XXXX: Self Describing Data Object Tags";
  }

  extension opm-tag {
    argument tag;

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    description
      "The argument 'tag' is of type 'tag'. This extension statement
       is used by module authors to indicate the opm tags that should be
       added automatically by the system. Opm Tag is used to classify
       operation and management data into object, property subobject, and metric
       subobject three categories. Object can contain other objects called subobjects.
       Property and metric objects are both subobjects belonging to specific object.
       Both object and subobjects can be modeled as data nodes. Object can be one of
       container, leaf-list and list. Property subobject is a leaf node. Metric subobject
       can be one of container, leaf-list, list, leaf. Object contains zero or many
       property subobjects, zero or many metric subobjects. As such the origin of the value
       for the pre-defined tags should be set to 'system'.";
  }
  extension metric-type {
    argument tag;
    description
      "The argument 'tag' is of type 'tag'.The metric-type can be
       used to provide metric subobject classification
       (e.g., loss, jitter, packet loss, guage, counter, histogram, unknow, etc.)
       within the YANG module.";
  }
  extension multi-source-tag {
    argument tag;
    description
      "The argument 'tag' is of type 'tag'.The multi-source-tag can be
       used to identify  multi-source aggregation type (e.g., aggregated,
       non-aggregated) related to metric subobject.

      'aggregated' multi-source aggregation type allows a large number of
      measurements on metric subobjects from different sources of the same
      type (e.g., line card, each subinterface of aggregated Ethernet interface)
      being combined into aggregated statistics and report as one metric subobject
      value. 'non-aggregated' multi-source aggregation type allows measurement from
      each source of the same type (e.g., line card, each subinterface of aggregated
      Ethernet interface) be reported separately.";
   }

  augment "/tags:module-tags/tags:module" {
    description
      "Augment the Module Tags module with data object tag attributes.";
    container data-object-tags {
      config false;
      status deprecated;
      description
        "Contains the list of data objects and their associated self describing tags.";
      list data-object {
        key "object-name";
        status deprecated;

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        description
          "A list of data objects and their associated self describing tags.";
        leaf object-name {
          type nacm:node-instance-identifier;
          mandatory true;
          status deprecated;
          description
            "The YANG data object name.";
        }
        leaf-list tag {
          type tags:tag;
          status deprecated;
          description
            "Tags associated with the data object within the YANG module. See
             the IANA 'YANG Data Object Tag Prefixes' registry for reserved
             prefixes and the IANA 'IETF YANG Data Object Tags' registry for
             IETF tags.

             The 'operational' state view of this list is
             constructed using the following steps:

             1) System tags (i.e., tags of 'system' origin) are added.
             2) User configured tags (i.e., tags of 'intended' origin)
             are added.
             3) Any tag that is equal to a masked-tag is removed.";
        }
        leaf-list masked-tag {
          type tags:tag;
          status deprecated;
          description
            "The list of tags that should not be associated with the data
             object within the YANG module. The user can remove (mask) tags from the
             operational state datastore by adding them to
             this list. It is not an error to add tags to this list
             that are not associated with the data object within YANG module,
             but they have no operational effect.";
        }
      }
    }
  }
}
<CODE ENDS>

Appendix C.  Targeted data object collection example

   The following provides targeted data object collection example which
   helps reduce amount of data to be fetched.  The subscription "id"

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   values of 22 used below is just an example.  In production, the
   actual values of "id" might not be small integers.

    +-----------+                       +-----------+
    | Subscriber|                       | Publisher |
    +------+----+                       +-----+-----+
           |                                  |
           |                                  |
           |Telemery data Tagging Advertisement
           |  (data object name, opm-tag = metric)
           |<---------------------------------|
           |                                  |
           |    establish-subscription        |
           |--------------------------------->|
           |                                  |
           |                                  |
           |    RPC Reply: OK, id = 22        |
           |<---------------------------------|
           |                                  |
           |                                  |
           |    Notification Message (for 22) |
           | <--------------------------------|
           |                                  |
           |                                  |

   The publisher advertises telemetry data object capability to the
   subscriber to instruct the receiver to subscribe tagged data object
   (e.g., performance metric data object) using standard subscribed
   notification mechanism [RFC8639].

   The following XML example [W3C.REC-xml-20081126] illustrates the
   advertisment of the list of available target objects using YANG
   instance file format [I-D.ietf-netmod-yang-instance-file-format]:

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<?xml version="1.0" encoding="UTF-8"?>
<instance-data-set xmlns=\
    "urn:ietf:params:xml:ns:yang:ietf-yang-instance-data">
  <name>acme-router-notification-capabilities</name>
  <content-schema>
    <module>ietf-system-capabilities@2020-03-23</module>
    <module>ietf-notification-capabilities@2020-03-23</module>
    <module>ietf-data-export-capabilities@2020-03-23</module>
  </content-schema>
  <!-- revision date, contact, etc. -->
  <description>Defines the notification capabilities of an acme-router.
    The router only has running, and operational datastores.
    Every change can be reported on-change from running, but
    only config=true nodes and some config=false data from operational.
    Statistics are not reported based on timer based trigger and counter
    threshold based trigger.
  </description>
  <content-data>
    <system-capabilities \
      xmlns="urn:ietf:params:xml:ns:yang:ietf-system-capabilities" \
      xmlns:inc=\
        "urn:ietf:params:xml:ns:yang:ietf-notification-capabilities" \
      xmlns:ds="urn:ietf:params:xml:ns:yang:ietf-datastores">
      <datastore-capabilities>
        <datastore>ds:operational</datastore>
        <per-node-capabilities>
          <node-selector>\
              /if:interfaces/if:interface/if:statistics/if:in-errors\
          </node-selector>
          <sec:self-describing-capabilities>
            <sec:opm-tag>metric</sec:opm-tag>
            <sec:metric-type>loss</sec:metric-type>
          </sec:self-describing-capabilities>
        </per-node-capabilities>
      </datastore-capabilities>
    </system-capabilities>
  </content-data>
</instance-data-set>

   With telemetry data tagging information carried in the Telemetry data
   Tagging Advertisement, the subscriber identifies targeted data object
   and associated data path to the datastore node and sends a standard
   establish-subscription RPC [RFC8639] to subscribe tagged data objects
   that are interests to the client application from the publisher.

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 <netconf:rpc message-id="101"
     xmlns:netconf="urn:ietf:params:xml:ns:netconf:base:1.0">
   <establish-subscription
       xmlns="urn:ietf:params:xml:ns:yang:ietf-subscribed-notifications"
       xmlns:yp="urn:ietf:params:xml:ns:yang:ietf-yang-push">
     <yp:datastore
          xmlns:ds="urn:ietf:params:xml:ns:yang:ietf-datastores">
       ds:operational
     </yp:datastore>
     <yp:datastore-xpath-filter
         xmlns:ex="https://example.com/sample-data/1.0">
       /if:interfaces/if:interface/if:statistics/if:in-errors
     </yp:datastore-xpath-filter>
     <yp:periodic>
       <yp:period>500</yp:period>
     </yp:periodic>
   </establish-subscription>
 </netconf:rpc>

   The publisher returns specific object type of operational state
   (e.g., in-errors statistics data) subscribed by the client.

Appendix D.  Changes between Revisions

   v02 - v03

   o  Additional Editorial changes.

   o  Security section enhancement.

   o  Nits fixed.

   v01 - v02

   o  Clarify the relation between data object, object tag, property tag
      and metric tag in figure 1 and figure 2 and related description;

   o  Change Metric Group into Metric Type in the YANG model;

   o  Add 5 metric types in section 7.2;

   v00 - v01

   o  Merge self describing data object tag use case section into
      introduction section as a subsection;

   o  Add one glossary section;

Wu, et al.              Expires November 14, 2021              [Page 26]
Internet-Draft              Data Object Tags                    May 2021

   o  Clarify the relation between data object, object tag, property tag
      and metric tag in Self Describing Data Object Tags Use Case
      section;

   o  Add update to RFC8407 in the front page.

Authors' Addresses

   Qin Wu
   Huawei
   101 Software Avenue, Yuhua District
   Nanjing, Jiangsu  210012
   China

   Email: bill.wu@huawei.com

   Benoit Claise
   Huawei
   De Kleetlaan 6a b1
   Diegem  1831
   Belgium

   Email: benoit.claise@huawei.com

   Peng Liu
   China Mobile
   32 Xuanwumen West St, Xicheng District
   Beijing  10053

   Email: liupengyjy@chinamobile.com

   Zongpeng Du
   China Mobile
   32 Xuanwumen West St, Xicheng District
   Beijing  10053

   Email: duzongpeng@chinamobile.com

   Mohamed Boucadair
   Orange
   Rennes 35000
   France

   Email: mohamed.boucadair@orange.com

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