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.

Status of This Memo

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   This Internet-Draft will expire on September 14, 2017.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Tree Diagram Syntax . . . . . . . . . . . . . . . . . . . . .   2
   3.  Next Steps  . . . . . . . . . . . . . . . . . . . . . . . . .   3
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   4
   5.  Informative References  . . . . . . . . . . . . . . . . . . .   4
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   4

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 <https://github.com/mbj4668/pyang>).  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.

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

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

   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

   Each node in a YANG module is printed as:

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   <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 "{...}?"

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.

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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., Ed., "The YANG 1.1 Data Modeling Language",
              RFC 7950, DOI 10.17487/RFC7950, August 2016,

Authors' Addresses

   Martin Bjorklund
   Tail-f Systems

   Email: mbj@tail-f.com

   Lou Berger (editor)
   LabN Consulting, L.L.C.

   Email: lberger@labn.net

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