Network Working Group M. Bjorklund
Internet-Draft Tail-f Systems
Intended status: Informational L. Berger, Ed.
Expires: September 14, 2017 LabN Consulting, L.L.C.
March 13, 2017

YANG Tree Diagrams


This document captures the current syntax used in YANG module Tree Diagrams. The purpose of the 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.

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Table of Contents

1. Introduction

YANG Tree Diagrams were first published in [RFC7223]. Such diagrams are commonly used to provided a simplified graphical representation of a data model and can be automatically generated via tools such as "pyang". (See <>). This document provides the syntax used in YANG Tree Diagrams. It is expected that this document will be updated or replaced as changes to the YANG language, see [RFC7950], necessitate.

Today's Common practice is 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 and the purpose of the 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 such changes are easily identified and suitably agreed upon.

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

An example tree diagram can be found in [RFC7223] Section 3. A portion of which follows:

The remainder of this document contains YANG Tree Diagram syntax based on output from pyang version 1.7.1.

2. Tree Diagram Syntax

This section provides the meaning of the symbols used in YANG Tree diagrams.

<status> <flags> <name> <opts> <type> <if-features>

  <status> is one of:
    +  for current
    x  for deprecated
    o  for obsolete

  <flags> is one of:
    rw  for configuration data
    ro  for non-configuration data
    -x  for rpcs and actions
    -n  for notifications

  <name> is the name of the node
    (<name>) means that the node is a choice node
   :(<name>) means that the node is a case node

   If the node is augmented into the tree from another module, its
   name is printed as <prefix>:<name>.

  <opts> is one of:
    ?  for an optional leaf, choice, anydata or anyxml
    !  for a presence container
    *  for a leaf-list or list
    [<keys>] for a list's keys

  <type> is the name of the type for leafs and leaf-lists

    If the type is a leafref, the type is printed as "-> TARGET",
    where TARGET is either the leafref path, with prefixed removed
    if possible.

  <if-features> is the list of features this node depends on,
  printed within curly brackets and a question mark "{...}?"


Each node in a YANG module is printed as:

3. Next Steps

Authors' note: This draft is currently a bit rough. The next/future version is expected to add text covering different types of trees and when to use them; for example, complete module trees, subtrees, trees for groupings etc. Maybe also how to deal with the limited line lengths in RFCs.

4. IANA Considerations

There are no IANA requests or assignments included in this document.

5. Informative References

[RFC7223] Bjorklund, M., "A YANG Data Model for Interface Management", RFC 7223, DOI 10.17487/RFC7223, May 2014.
[RFC7950] Bjorklund, M., "The YANG 1.1 Data Modeling Language", RFC 7950, DOI 10.17487/RFC7950, August 2016.

Authors' Addresses

Martin Bjorklund Tail-f Systems EMail:
Lou Berger (editor) LabN Consulting, L.L.C. EMail: