NETCONF Data Modeling Language L. Bertz
Internet-Draft Sprint
Intended status: Standards Track March 9, 2017
Expires: September 10, 2017
YANG extension for Common Augmentations
draft-bertz-netmod-commonaugment-01
Abstract
This document defines a YANG extension to convey common schema
augmentations.
Status of This Memo
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This Internet-Draft will expire on September 10, 2017.
Copyright Notice
Copyright (c) 2017 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.
This document may contain material from IETF Documents or IETF
Contributions published or made publicly available before November
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10, 2008. The person(s) controlling the copyright in some of this
material may not have granted the IETF Trust the right to allow
modifications of such material outside the IETF Standards Process.
Without obtaining an adequate license from the person(s) controlling
the copyright in such materials, this document may not be modified
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not be created outside the IETF Standards Process, except to format
it for publication as an RFC or to translate it into languages other
than English.
1. Introduction
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 [RFC7950].
YANG extensions commonly add one augmentation to a common structure.
Figure 1 shows a small module and another that will be used to extend
it.
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... basemodule {
prefix b;
...
grouping base_element {
...
}
rpc my_rpc {
input {
uses b:base_element;
}
output {
uses b:base_element;
}
}
rpc my_bestrpc {
input {
uses b:base_element;
}
}
}
... newstuffmodule {
grouping new_things {
...
}
}
Figure 1: Reference Modules
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.
Figure 2 shows the traditional and common augment examples.
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module old_way {
import base { prefix base_module; }
import newstuff { prefix new_module; }
augment "/base_module:my_rpc/base_element/input" {
uses new_module:new_things;
}
augment "/base_module:my_rpc/base_element/output" {
uses new_module:new_things;
}
augment "/base_module:my_bestrpc/base_element/input" {
uses new_module:new_things;
}
}
module new_way {
import base { prefix base_module; }
import newstuff { prefix new_module; }
import commonaugment { prefix c; }
augment "/base_module:my_rpc/base_element/input" {
uses new_module:new_things;
c:also-augments "/base_module:my_rpc/base_element/output";
c:also-augments "/base_module:my_bestrpc/base_element/input";
}
}
Figure 2: Augment Options
The also-augments statement takes a single argument that is the same
one defined for the augment statement [RFC7950].
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.
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2. Requirements Language
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 [RFC2119].
3. Overview
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 Figure 3.
augment "/base_module:my_rpc/base_element/input" {
uses new_module:new_things;
}
augment "/base_module:my_rpc/base_element/output" {
uses new_module:new_things;
}
... semantically equivalent version below ...
augment "/base_module:my_rpc/base_element/input" {
uses new_module:new_things;
c:also-augments "/base_module:my_rpc/base_element/output";
}
Figure 3: Statement Equivalence of also-augments
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 Figure 4. 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.
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augment "/base_module:my_rpc/base_element/input" {
uses new_module:new_things;
c:also-augments "/base_module:my_rpc/base_element/output";
}
augment "/base_module:my_rpc/base_element/output" {
uses new_module:new_things;
}
Figure 4: Backwards compatible usage of also-augment
4. Module Definition
This section contains the module definition.
<CODE BEGINS> 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: <http://tools.ietf.org/wg/netmod/>
WG List: <mailto:netmod@ietf.org>
WG Chair: Lou Berger
<mailto:lberger@labn.net>
WG Chair: Kent Watsen
<mailto:kwatsen@juniper.net>
Editor: Lyle Bertz
<mailto:lyleb551144@gmail.com>";
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
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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";
}
}
<CODE ENDS>
5. IANA Considerations
This document registers six URIs in the "IETF XML Registry"
[RFC3688]. 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
6. Security Considerations
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.
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7. References
7.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
[RFC7950] Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language",
RFC 7950, DOI 10.17487/RFC7950, August 2016,
<http://www.rfc-editor.org/info/rfc7950>.
7.2. Informative References
[RFC3688] Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,
DOI 10.17487/RFC3688, January 2004,
<http://www.rfc-editor.org/info/rfc3688>.
Author's Address
Lyle Bertz
Sprint
6220 Sprint Parkway
Overland Park, KS 66251
United States
Email: lylebe551144@gmail.com
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