...

Sample YANG

(stores.yang with extension)

Statements and Description

Code Block

language	yml
title	stores model with extension
linenumbers	true

module stores {
…
prefix book-store;
…
   extension sampleExtensionsync-flag{
     description
           “This is a sample extension statement description“
      argument name {
          yin-element true"value";
     }
   }
container bookstore { 
        leaf bookstore-name {
            type string;
        }
….
}

Code Block

language	yml
title	exampleextended-module2 stores model
linenumbers	true

module example-module2{
…
     import extended-stores {
       prefix book-store;yang-version 1.1;
	...
    import }stores{

	    prefix book-store:sampleExtension locations {
       list address {
         key "state";;
	}

         leaf statetypedef year {
           type string;
           description "State name"uint16 {
               book-store:sampleExtension-b "b-sample-namerange "1000..9999";
           }
         }
         leaf city {
           type string;
    container       description "City name"{
       bookstore {
        book-store:sampleExtensionsync-cflag "c-sample-nameon";
           }
….
   }


...
	}
}

extension Statement

see example from Lines 5-11 9 on stores model with extension

Syntax

Code Block

language	text

extension <keyword/identifier>{
     <extension substatements...>
}

Usage

see example from Lines Line 15 on extended-stores model

Code Block

language	text

<module prefix>:<extension keyword> "argument";

to be used to define new statements
available to be imported and used by other modules just like a normal YANG statement
- - by use of 'import statement' to import the module where the extension is defined
statements that do not have any substatements can have extensions defined if wanted
its only one argument is the identifier and keyword for the extension
Optional substatements:
- - argument Statement
  - description Statement
  - reference Statement
  - defined extension Statements

argument Statement

see examples from Lines Line 6 on stores model

takes a string argument which is the name of the argument to the keyword
Optional substatement
- - yin-element Statement

Code Block

language	xml
theme	Midnight
title	exampleYIN-extended-model2 stores model (YIN version)
linenumbers	true

<?xml version="1.0" encoding="UTF-8"?>
<module name="exampleextended-module2stores"
        xmlns="urn:ietf:params:xml:ns:yang:yin:1"
        xmlns:emext-book-store="org:onap:ccsdk:sample2sampleExtended"
        xmlns:book-store="org:onap:ccsdk:sample">
  <yang-version value="1.1"/>
  <namespace uri="org:onap:ccsdk:sample2sampleExtended"/>
  <prefix value="emext-book-store"/>
  <import<revision moduledate="stores2020-09-15">
    <description>
   <prefix value="book-store"/>
  </import>
<text>Sample  <book-store:sampleExtension>Extended Model</text>
    <book-store:name>locations</book-store:name></description>
  </revision>
  <list<import namemodule="addressstores">
      <key<prefix value="statebook-store"/>
  </import>
    <leaf<typedef name="stateyear">
        <type name="stringuint16"/>
        <description><range value="1000..9999"/>
    </type>
      <text>State name</text></typedef>
  <container name="bookstore">
       <book-store:sampleExtensionsync-bflag namevalue="b-sample-nameon"/>
        </description>
      </leaf>
      <leaf name="citybookstore-name">
        <type name="string"/>
        <description>
          <text>City name</text>
          <book-store:sampleExtension-c>
            <book-store:name>c-sample-name</book-store:name>
          </book-store:sampleExtension-c>
        </description>
      </leaf>
    </list>leaf>
	...
  </book-store:sampleExtension>container>
</module>

yin-element Statement

takes a string argument which is true or false
yin-element is 'false' by default
if the argument is 'true' it indicates that the argument is mapped to an XML element in YIN or to an XML attribute

Line

** the YIN version and Schema trees above are generated by YANG validator 'pyang'

Expected tree diagram for example-module based on RFC8340 (https://datatracker.ietf.org/doc/html/rfc8340):

...

language	text
title	Schema tree for sampleExtension

Notes

Line 22 on YIN-extended-stores model
1. result of using the argument without specifying the yin-element value
  1. yin-element is 'false'
  2. the argument 'value' is only an XML attribute
if argument statement (Line 6 on stores model) contains yin-element substatement YIN-extend-stores model would result to the following:
1. extension statement will produce a child node
  Code Block
  theme Midnight
  title YIN-extended-stores model where yin-element is 'true'
  ... <container name="bookstore"> <book-store:sync-flag>

...

<book-store:value>on</book-store:value>

...

</book-store:sync-flag>
...
  </container>
...

** the YIN version and Schema trees above are generated by YANG validator 'pyang'

Existing YANG parser in CPS

(Please see https://wiki.onap.org/display/DW/Existing+Yang+Parser)

OpenDayLight Yang tools recognises recognise YANG extensions

Contains interface which has methods to access data of a YANG extension statement

Code Block

language	java
theme	Eclipse
title	Yang tools ExtensionDefinition Interface

package org.opendaylight.yangtools.yang.model.api;
import org.opendaylight.yangtools.yang.model.api.stmt.ExtensionEffectiveStatement;
public interface ExtensionDefinition extends SchemaNode, EffectiveStatementEquivalent<ExtensionEffectiveStatement> {
    String getArgument();
    boolean isYinElement();
}

Implementing ClassClass

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Existing YANG parser in CPS

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Versions Compared

Old Version 14

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Key

Existing YANG parser in CPS