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

      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>
      ...

• extension defined as substatement in the module with argument statement as its substatement
• extension used inside container statement before all other substatements
• extension contained argument

module stores {
    yang-version 1.1;
	...
    extension sync-flag{
        description "This extension allows to tag nodes with a sync flag";
        argument "value";
    }

    typedef year {...}

    container bookstore {
        book-store:sync-flag "on";
		...
        leaf bookstore-name {...}
		list categories {..}
...
}

• extension declared after all other substatements of container still passed

• extension defined as substatement in the module with argument statement as its substatement
• extension used inside a leaf statement (child of a container) before all other substatements
• extension contained argument

module stores {
    yang-version 1.1;
	...
    extension sync-flag{
        description "This extension allows to tag nodes with a sync flag";
        argument "value";
    }

    typedef year {...}

    container bookstore {
		...
        leaf bookstore-name {
	      book-store:sync-flag "on"; 
		}
		list categories {..}
...
}

• extension defined as substatement in the module with argument statement as its substatement
• extension used inside list statement (child of a container) before all other substatements
• extension contained argument

module stores {
    yang-version 1.1;
	...
    extension sync-flag{
        description "This extension allows to tag nodes with a sync flag";
        argument "value";
    }

    typedef year {...}

    container bookstore {
		...
        leaf bookstore-name {...}
		list categories {
		 	book-store:sync-flag "on";
			key "code";
			...  
		}
...
}

• extension defined as substatement in the module with argument statement as its substatement
• extension used inside leaf statement (child of list node from case #3) before all its substatements
• extension contained argument

module stores {
    yang-version 1.1;
 	...
    extension sync-flag{
        description "This extension allows to tag nodes with a sync flag";
        argument "value";
    }
    typedef year {...}

    container bookstore {
        leaf bookstore-name {...}

    list categories {
        key "code";
        leaf code {
            book-store:sync-flag "on";
            type string;
        }
        leaf name {...}
        list books {...}
...
}

• extension defined as substatement in the module with argument statement as its substatement
• extension used inside list node (child of list node from case #4) before key-statement of list
• extension contained argument

module stores {
    yang-version 1.1;
 	...
    extension sync-flag{
        description "This extension allows to tag nodes with a sync flag";
        argument "value";
    }
    typedef year {...}

    container bookstore {
        leaf bookstore-name {...}

    list categories {
        key "code";
        leaf code {...}
        leaf name {...}
        list books {
		 book-store:sync-flag "on";
		...
		}
...
}

• extension defined as substatement in the module with argument statement as its substatement
• extension used inside leaf-list node (child of list node from case #5) before all other substatements
• extension contained argument

module stores {
    yang-version 1.1;
 	...
    extension sync-flag{
        description "This extension allows to tag nodes with a sync flag";
        argument "value";
    }
    typedef year {...}

    container bookstore {
        leaf bookstore-name {...}

    list categories {
        key "code";
        leaf code {...}
        leaf name {...}
        list books {
			leaf-list authors{
			  book-store:sync-flag "on"; 
			}
		}
...
}

• extension defined as substatement in the module with argument statement as its substatement
• extension used inside module
• extension declared before container node
• extension contained argument

module stores {
    yang-version 1.1;
	...
    extension sync-flag{
        description "This extension allows to tag nodes with a sync flag";
        argument "value";
    }

    typedef year {...}

    book-store:sync-flag "on"; 

    container bookstore {...}
}

• scenario the same as case 1 but the extension was used in the container statement without an argument

module stores {
    yang-version 1.1;
	...
    extension sync-flag{
        description "This extension allows to tag nodes with a sync flag";
        argument "value";
    }

    typedef year {...}

    container bookstore {
        book-store:sync-flag;
		...
}

• extension defined as substatement in the module without argument statement as its substatement
• extension used inside container statement before all other substatements
• extension declared has no argument

module stores {
    yang-version 1.1;
	...
    extension sync-flag;

    typedef year {...}

    container bookstore {
        book-store:sync-flag;
		...
        leaf bookstore-name {...}
		list categories {..}
...
}

• extension defined as substatement in the module without argument statement as its substatement
• extension used twice
  • inside container statement before all other substatements
  • inside leaf statement (child of container statement)
• extension declared has no argument

module stores {
    yang-version 1.1;
	...
    extension sync-flag;

    typedef year {...}

    container bookstore {
        book-store:sync-flag;
		...
        leaf bookstore-name {
			book-store:sync-flag;
		}
		list categories {..}
...
}