YANG extension for Common Augmentations

This document provides a mechanism for the specification of an augmentation at multiple locations of a YANG schema using the extension statement as defined in Section 7.15 of . YANG extensions commonly add one augmentation to a common structure. shows a small module and another that will be used to extend it.

When extending my_rpc in the base module by adding new_things to the base element, one must use two augment statements. If the author of the newstuff module wishes to extend base_element then they must write an augment statement for every schema location it which it appears. An extension with the key word "also-augments" is proposed that allows one augment statement to be used for augmentations. shows the traditional and common augment examples.

The also-augments statement takes a single argument that is the same one defined for the augment statement . This has two purposes: Reduces the amount of YANG written when common augmentations are invovled. Provides a hint to the tools that translate YANG to code that a common augmentation exists. The importance of the second benefit for is significant as it permits them to leverage any common structure or inheritence functions.

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119.

This module defines only the also-augmennts extension. This extension is ONLY meaningful as a child of an augment statement and is otherwise ignored. It is semantically equivalent to writing an augment statement whose target node is the argument of the also-augment node. This is shown in .

Multiple also-augments statements MAY appear in a single augment statement. This statement MAY appear in a module that is intended to be backwards compatible as shown in . In such cases, it is used as a hint to readers and compilation software that the augmentations are intended to be the same augmentation at multiple schema tree locations.

This section contains the module definition.

file "ietf-commonaugment@2017-03-04.yang" module ietf-commonaugment { yang-version 1.1; namespace "urn:ietf:params:xml:ns:yang:ietf-commonaugment"; prefix commonaug; organization "IETF NETMOD (NETCONF Data Modeling Language) Working Group"; contact "WG Web: WG List: WG Chair: Lou Berger WG Chair: Kent Watsen Editor: Lyle Bertz "; description "This module contains YANG definition for common augments. Copyright (c) 2016 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License."; revision 2017-03-04 { description "Initial Revision."; reference "draft-bertz-netmod-commonaugment-00"; } extension also-augments { argument "target-node"; description "The argument is a string that identifies a node in the schema tree and is the same argument that is defined for the YANG argument statement"; } } ]]>


   

  This document registers six URIs in the "IETF XML Registry"
   .  Following the format in RFC 3688, the following
   registrations have been made.

  
   URI: urn:ietf:params:xml:ns:yang:commonaug
   Registrant Contact: The NETMOD WG of the IETF.
   XML: N/A, the requested URI is an XML namespace.

  This document registers the following YANG module in the "YANG
    Module Names" registry [RFC7950].

  
        name:         ietf-dmm-fpc
        namespace:    urn:ietf:params:xml:ns:yang:commonaug
        prefix:       commonaug
        reference:    TBD1
  


   

   This document provides an alternative mechanism to express augmentations
   that can exist in a YANG module.  It does not provide new informaiton
   elements to the module but does provide a hint as to the commonality of
   a set of augment statements.  This, however, SHOULD have already been
   described in the module's definition or specification.  Thus, the use
   of this statement does not yield new information.