YANG Tree Diagrams
RFC 8340

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Internet Engineering Task Force (IETF)                      M. Bjorklund
Request for Comments: 8340                                Tail-f Systems
BCP: 215                                                  L. Berger, Ed.
Category: Best Current Practice                  LabN Consulting, L.L.C.
ISSN: 2070-1721                                               March 2018

                           YANG Tree Diagrams

Abstract

   This document captures the current syntax used in YANG module tree
   diagrams.  The purpose of this document is to provide a single
   location for this definition.  This syntax may be updated from time
   to time based on the evolution of the YANG language.

Status of This Memo

   This memo documents an Internet Best Current Practice.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Further information on
   BCPs is available in Section 2 of RFC 7841.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   https://www.rfc-editor.org/info/rfc8340.

Copyright Notice

   Copyright (c) 2018 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.

Bjorklund & Berger        Best Current Practice                 [Page 1]
RFC 8340                   YANG Tree Diagrams                 March 2018

Table of Contents

   1. Introduction ....................................................2
   2. Tree Diagram Syntax .............................................3
      2.1. Submodules .................................................5
      2.2. Groupings ..................................................5
      2.3. yang-data ..................................................5
      2.4. Collapsed Node Representation ..............................6
      2.5. Comments ...................................................6
      2.6. Node Representation ........................................6
   3. Usage Guidelines for RFCs .......................................7
      3.1. Wrapping Long Lines ........................................8
      3.2. Groupings ..................................................8
      3.3. Long Diagrams ..............................................8
   4. YANG Schema Mount Tree Diagrams .................................9
      4.1. Representation of Mounted Schema Trees ....................10
   5. IANA Considerations ............................................12
   6. Security Considerations ........................................12
   7. Informative References .........................................12
   Authors' Addresses ................................................13

1.  Introduction

   YANG tree diagrams were first published in RFC 6536.  Such diagrams
   are used to provide a simplified graphical representation of a data
   model and can be automatically generated via tools such as "pyang"
   [PYANG].  This document describes the syntax used in YANG tree
   diagrams.  It is expected that this document will be updated or
   replaced as changes to the YANG language [RFC7950] necessitate.

   Today's common practice is to include the definition of the syntax
   used to represent a YANG module in every document that provides a
   tree diagram.  This practice has several disadvantages; therefore,
   the purpose of this document is to provide a single location for this
   definition.  It is not the intent of this document to restrict future
   changes, but rather to ensure that such changes are easily identified
   and suitably agreed upon.

   An example tree diagram can be found in Section 3 of [RFC8343]; the
   following is a portion of it:

     +--rw interfaces
        +--rw interface* [name]
           +--rw name                        string
           +--rw description?                string
           +--rw type                        identityref
           +--rw enabled?                    boolean
           +--rw link-up-down-trap-enable?   enumeration {if-mib}?

Bjorklund & Berger        Best Current Practice                 [Page 2]
RFC 8340                   YANG Tree Diagrams                 March 2018

2.  Tree Diagram Syntax

   This section describes the meaning of the symbols used in YANG tree