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Sample YANG

(stores.yang with extension)

Statements and Description

Code Block

language	yml
title	stores model with extension
linenumbers	true

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.

Code Block

language	yml
title	extended-stores model
linenumbers	true

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

Code Block

language	text

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

Usage

see example from 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 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	YIN-extended-stores model
linenumbers	true

<?xml version="1.0" encoding="UTF-8"?>
<module name="extended-stores"
        xmlns="urn:ietf:params:xml:ns:yang:yin:1"
        xmlns:ext-book-store="org:onap:ccsdk:sampleExtended"
        xmlns:book-store="org:onap:ccsdk:sample">
  <namespace uri="org:onap:ccsdk:sampleExtended"/>
  <prefix value="ext-book-store"/>
  <revision date="2020-09-15">
    <description>
      <text>Sample Extended Model</text>
    </description>
  </revision>
  <import module="sync-extension">
    <prefix value="sync-ext"/>
  </import>
  <typedef name="year">
    <type name="uint16">
      <range value="1000..9999"/>
    </type>
  </typedef>
  <container name="bookstore">
    <sync-ext:sync-flag value="on"/>
    <leaf name="bookstore-name">
      <type name="string"/>
    </leaf>
	...
  </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

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:

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

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

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The YANG language extension analysis above is only applicable for seeing that it is good for type informationconfiguration.
- Extension The extension does not extend the actual data of the model instance
- Based on the test scenarios above, extensions can only be seen on the schema sets and not on the data
YANG extension can be used at every level of the tree model
The test results show that the model is being recognized by the current YANG tools used to parse a model
- It fails for scenarios such as parsing a model without an argument defined when it is expecting it
This analysis did not look further into the effect of setting yin-element to 'true' for the model instance
Further investigation is required to cover interpretation as the analysis above only covers parsing
- see
  Jira
  server ONAP Jira
  serverId 425b2b0a-557c-3c0c-b515-579789cceedb
  key CPS-866

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