module sync-extension {
…
prefix sync-ext;
…
   extension sync-flag{
     description
           “This is a sample extension statement description“
      argument "value";
   }
….
}

The following model shows that it imported the model above where extensions is declared.

module extended-stores {
    yang-version 1.1;
	...
    import sync-extension{
	    prefix sync-ext;
	}

    typedef year {
        type uint16 {
            range "1000..9999";
        }
    }

    container bookstore {
       sync-ext:sync-flag "on";
    ...
	}
}
  

extension Statement

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

• Syntax

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

• Usage

see example from Line 15 on extended-stores model

<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

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

Notes

1. 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
2. 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"> <sync-ext:sync-flag> <sync-ext:value>on</sync-ext:value> </sync-ext:sync-flag> ... </container> ...

      ** this extension does not extend the data