module stores {
    yang-version 1.1;
    namespace "org:onap:ccsdk:sample";

    prefix book-store;

    revision "2020-09-15" {
        description
        "Sample Model";
    }

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

    container bookstore { 

        leaf bookstore-name {
            type string;
        }
    list categories {

        key "code";

        leaf code {	
            type string;
        }

        leaf name {
            type string;
        }

        list books {
            key title;

            leaf title {
                type string;
            }
            leaf-list authors {
                type string; 
            }
        }
    }
    }
}

module: stores
  +--rw bookstore
     +--rw bookstore-name?   string
     +--rw categories* [code]
        +--rw code     string
        +--rw name?    string
        +--rw books* [title]
           +--rw title       string
           +--rw lang?       string
           +--rw authors*    string
        

   +--rw pub_year? 

year
         

 +--rw price?      

uint64

module sync-extension {
…
prefix sync-ext;
…
   extension sync-flag{
   

 description
       

    “This is a sample extension statement 

description“

     argument "value";
   }

}

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 <keyword/identifier>{
     <extension 

substatements...>
}

module: stores
  +--rw bookstore
     +--rw bookstore-name?   string
     +--rw categories* [code]
        +--rw code     string
        +--rw name?    string
        +--rw books* [title]
           +--rw title       string
           +--rw lang?       string
           +--rw authors*    string
           +--rw pub_year?   year
           +--rw price?      uint64

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

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

<?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>

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

Existing YANG parser in CPS

(Please see https://lf-onap.atlassian.net/wiki/display/DW/Existing+Yang+Parser)

OpenDayLight Yang tools recognize 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(); }

  
  

Test cases and scenarios

The following test cases used and modified the standard stores model seen above.

Testing with groovy

The following cases were tested in YangTextSchemaSourceSetSpec.groovy using the test method 'Building a valid YangTextSchemaSourceSet using #filenameCase filename)'.

Key

**Green cell for case number indicates that tests have passed

**Red cell for case number indicates that tests have failed

• the extension is defined as substatement in the module with argument statement as its substatement

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 {..}
...
}

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 {

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

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

book-store:sync-flag "on"; 
		}
		list categories {..}
...
}

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";
			...  
		}
...
}

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 {...}

...
}

module stores {
    

** 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):

sampleExtension locations:
     +-- address* [state]
        +-- state string
        +-- city? string

Existing YANG parser

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

OpenDayLight Yang tools recognises YANG extensions

...

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();
}

...

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";
		...
		}
...
}

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"; 
			}
		}
...
}

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 {...}
}

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;
		...
}

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

    typedef year {...}

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

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 {..}
...
}

Extra Notes:

• There seems to be no inheritance of the extension statement for the substatements wherein the extension was used
• The date tree and schema tree does not change sizes with the addition of the extensions for all cases shown above

Parsing a original data instance (json) using the extended model

Conclusions

• The YANG language extension analysis above is only applicable for seeing that it is good for type configuration.
  • 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 Legacy
    server System Jira serverId 4733707d-2057-3a0f-ae5e-4fd8aff50176 key CPS-866