One document matched: draft-ietf-netmod-yang-metadata-01.xml
<?xml version="1.0"?>
<?rfc strict="yes"?>
<?rfc toc="yes"?>
<?rfc tocdepth="3"?>
<?rfc symrefs="yes"?>
<?rfc sortrefs="yes"?>
<?rfc compact="yes"?>
<?rfc subcompact="no"?>
<rfc docName="draft-ietf-netmod-yang-metadata-01" ipr="trust200902" category="std" obsoletes="" updates="" submissionType="IETF" xml:lang="en">
<front>
<title abbrev="YANG Metadata">Defining and Using Metadata with YANG</title>
<author fullname="Ladislav Lhotka" initials="L." surname="Lhotka">
<organization>CZ.NIC</organization>
<address>
<email>lhotka@nic.cz</email>
</address>
</author>
<date day="10" month="June" year="2015"/>
<area>ops</area>
<area>Operations and Management</area>
<workgroup>NETMOD Working Group</workgroup>
<abstract>
<t>This document defines a YANG extension statement that allows
for defining syntax of metadata annotions in YANG modules. The
document also specifies XML and JSON encoding of annotations and
other rules for annotating instances of YANG data nodes.</t>
</abstract>
</front>
<middle>
<section anchor="introduction" title="Introduction" toc="default">
<t>There is a need to be able to annotate instances of
YANG <xref target="I-D.ietf-netmod-rfc6020bis" pageno="false" format="default"/> data nodes with metadata. Typical
use cases are:
<list style="symbols">
<t>Deactivating a subtree in a configuration datastore while
keeping the data in place.</t>
<t>Complementing data model information with instance-specific
data.</t>
<t>RPC operations may use metadata annotations for various
purposes in both requests and responses. For example, the
<edit-config> operation in the NETCONF protocol (see
section 7.2 of <xref target="RFC6241" pageno="false" format="default"/>) uses annotations in
the form of XML attributes for identifying the point in the
configuration and type of the operation.</t>
</list></t>
<t>However, metadata annotations could potentially lead to
interoperability problems if they are used in an ad hoc fashion
by different organizations and/or without proper
documentation. A sound metadata framework for YANG should
therefore satisfy these requirements:
<list style="numbers">
<t>The set of annotations must be extensible in a distributed
manner so as to allow for defining new annotations without
running into the risk of collisions with annotations defined
and used by others.</t>
<t>Syntax and semantics of annotations must be documented and
the documentation must be easily accessible.</t>
<t>Clients of network management protocols such as
NETCONF <xref target="RFC6241" pageno="false" format="default"/> or RESTCONF <xref target="I-D.ietf-netconf-restconf" pageno="false" format="default"/> must be able to learn all
annotations supported by a given server and identify each of
them correctly.</t>
</list></t>
<t>This document proposes a systematic way for defining the
syntax of metadata annotations. For this purpose, YANG extension
statement "annotation" is defined in the module
"ietf-yang-metadata" (<xref target="ietf-yang-metadata" pageno="false" format="default"/>). Other YANG modules importing
this module can use the "annotation" statement for defining the
syntax of one or more annotations.</t>
<t>The benefits of defining the syntax of metadata annotations
in a YANG module are the following:
<list style="symbols">
<t>Each annotation is bound to a YANG module name, namespace
URI and prefix. This makes its encoding in instance documents
(both XML and JSON) straightforward and consistent with the
encoding of YANG data node instances.</t>
<t>Annotations are indirectly registered through IANA YANG
module registration.</t>
<t>Annotations are included in the data model. YANG compilers
and tools supporting a certain annotation can thus take them
into account and modify their behaviour accordingly.</t>
<t>An annotation can be declared as conditional by using the
"if-feature" statement.</t>
<t>Values of annotations are not limited to strings; any YANG
built-in or derived type may be used for them.</t>
</list></t>
</section>
<section anchor="terminology" title="Terminology" toc="default">
<t>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 <xref target="RFC2119" pageno="false" format="default"/>.</t>
<t>The following terms are defined in <xref target="RFC6241" pageno="false" format="default"/>:
<list style="symbols">
<t>client,</t>
<t>datastore,</t>
<t>message,</t>
<t>operation,</t>
<t>server.</t>
</list></t>
<t>The following terms are defined in <xref target="I-D.ietf-netmod-rfc6020bis" pageno="false" format="default"/>:
<list style="symbols">
<t>anydata,</t>
<t>anyxml,</t>
<t>built-in type,</t>
<t>derived type,</t>
<t>container,</t>
<t>data model,</t>
<t>data node,</t>
<t>derived type,</t>
<t>extension,</t>
<t>leaf-list,</t>
<t>list,</t>
<t>module,</t>
<t>RPC operation,</t>
<t>submodule,</t>
<t>type.</t>
</list></t>
<t>The following terms are defined in <xref target="W3C.REC-xml-infoset-20040204" pageno="false" format="default"/>:
<list style="symbols">
<t>attribute,</t>
<t>document,</t>
<t>element,</t>
<t>namespace,</t>
<t>prefix.</t>
</list></t>
<t>The following terms are defined in <xref target="RFC7159" pageno="false" format="default"/>:
<list style="symbols">
<t>array,</t>
<t>member,</t>
<t>object,</t>
<t>primitive type.</t>
</list></t>
<t>In the following text, XML element names and YANG extension
statements are always written with explicit namespace prefixes
that are assumed to be bound to URI references as shown in <xref target="tab.ns" pageno="false" format="default"/>.</t>
<texttable anchor="tab.ns" title="Used namespace prefixes and corresponding URI references" suppress-title="false" align="center" style="full">
<ttcol align="left">Prefix</ttcol>
<ttcol align="left">URI Reference</ttcol>
<c>rng</c>
<c>http://relaxng.org/ns/structure/1.0</c>
<c>md</c>
<c>urn:ietf:params:xml:ns:yang:ietf-yang-metadata</c>
<c>ein</c>
<c>http://example.org/example-inactive</c>
</texttable>
</section>
<section anchor="annotdef" title="Defining Annotations in YANG" toc="default">
<t>Metadata annotations are defined by YANG extension statement
"md:annotation". This YANG language extension is defined in the
module "ietf-yang-metadata" (<xref target="ietf-yang-metadata" pageno="false" format="default"/>).</t>
<t>Substatements of "md:annotation" are shown in <xref target="tab.annsub" pageno="false" format="default"/>. They are all core YANG statements, and
the numbers in the second column refer to the corresponding
sections in <xref target="I-D.ietf-netmod-rfc6020bis" pageno="false" format="default"/> where each
statement is described.</t>
<texttable anchor="tab.annsub" title="Substatements of "md:annotation"." suppress-title="false" align="center" style="full">
<ttcol align="left">substatement</ttcol>
<ttcol align="left">RFC 6020bis section</ttcol>
<ttcol align="left">cardinality</ttcol>
<c>description</c><c>7.20.3</c><c>0..1</c>
<c>if-feature</c><c>7.19.2</c><c>0..n</c>
<c>reference</c><c>7.20.4</c><c>0..1</c>
<c>status</c><c>7.20.2</c><c>0..1</c>
<c>type</c><c>7.6.3</c><c>0..1</c>
<c>units</c><c>7.3.3</c><c>0..1</c>
</texttable>
<t>Using the "type" statement, a type may be specified for the
annotation value according to the same rules as for YANG leaf or
leaf-list types. However, the "type" statement is optional as a
substatement of "md:annotation" statement. If it is not present,
the built-in "string" type is the default.</t>
<t>The "if-feature" statement, if present, makes the annotation
conditional: it is supported only by servers that advertise the
corresponding feature.</t>
<t>For example, the following module defines the "inactive"
annotation:</t>
<figure title="" suppress-title="false" align="left" alt="" width="" height="">
<artwork xml:space="preserve" name="" type="" align="left" alt="" width="" height="">
module example-inactive {
namespace "http://example.org/example-inactive";
prefix "ein";
import ietf-yang-metadata {
prefix "md";
}
md:annotation inactive {
type boolean;
description
"If this annotation is attached to a configuration data node,
then the data subtree rooted at this node is deactivated.";
}
}
</artwork>
</figure>
<t>By advertising a YANG module in which metadata annotation A
is defined using the "md:annotation" statement, a server
specifies support for the syntax of annotation A. This means
that configuration or state data, RPC messages and notifications
will be considered syntactically valid if annotation A is
attached to any data node instance, provided that all rules
stated in this document are observed.</t>
<t>However, the semantics of an annotation, usage rules, and
expected behavior of clients and servers MUST be specified
separately by other means that are outside the scope of this
document.</t>
</section>
<section anchor="encoding" title="The Encoding of Annotations" toc="default">
<t>XML attributes are a natural choice for encoding metadata in
XML instance documents. For JSON <xref target="RFC7159" pageno="false" format="default"/>, there
is no generally established method for encoding metadata. This
document thus introduces a special encoding method that is
consistent with the JSON encoding of YANG data node instances as
defined in <xref target="I-D.ietf-netmod-yang-json" pageno="false" format="default"/>.</t>
<section anchor="enc-xml" title="XML Encoding" toc="default">
<t>Metadata annotations are added to XML-encoded instances of
YANG data nodes as XML attributes according to these rules:
<list style="symbols">
<t>The local name of the attribute SHALL be the same as the
name of the annotation specified in the argument of the
corresponding "md:annotation" statement.</t>
<t>The namespace of the attribute SHALL be identified by the
URI that appears as the argument of the "namespace"
statement in the YANG module where the annotation is
defined. It is RECOMMENDED that the prefix specified by the
"prefix" statement in the same module is used in the
qualified name of the attribute.</t>
<t>The attribute value SHALL be encoded in the same way as
the value of a YANG leaf instance having the same type,
see <xref target="I-D.ietf-netmod-rfc6020bis" pageno="false" format="default"/>, sec. 9.</t>
</list></t>
<t>For example, the "inactive" annotation defined in <xref target="annotdef" pageno="false" format="default"/> may be encoded as follows:</t>
<figure title="" suppress-title="false" align="left" alt="" width="" height="">
<artwork xml:space="preserve" name="" type="" align="left" alt="" width="" height="">
<foo xmlns:ein="http://example.org/example-inactive"
ein:inactive="true">
...
</foo></artwork>
</figure>
</section>
<section anchor="enc-json" title="JSON Encoding" toc="default">
<t>The JSON metadata encoding defined in this section has the
following properties:
<list style="numbers">
<t>The encoding of YANG data node instances as defined in
<xref target="I-D.ietf-netmod-yang-json" pageno="false" format="default"/> does not change.</t>
<t>Namespaces of metadata annotations are encoded in the same
way as namespaces of YANG data node instances, see <xref target="I-D.ietf-netmod-yang-json" pageno="false" format="default"/>.</t>
</list></t>
<section anchor="met-obj" title="Metadata Object and Annotations" toc="default">
<t>All metadata annotations assigned to a YANG data node
instance are encoded as members (name/value pairs) of a
single JSON object, henceforth denoted as the metadata
object. The placement and name of this object depends on the
type of the data node as specified in the following
subsections.</t>
<t>The name of a metadata annotation (as a member of the
metadata object) SHALL be of the following form:
<figure title="" suppress-title="false" align="left" alt="" width="" height="">
<artwork xml:space="preserve" name="" type="" align="left" alt="" width="" height="">MODULE_NAME:LOCAL_NAME</artwork>
</figure>
where MODULE_NAME is the name of the YANG module in which
the annotation is defined, and LOCAL_NAME is the name of the
annotation specified in the argument of the corresponding
"md:annotation" statement.</t>
<t>Note that unlike YANG data node instances, for
annotations the explicit namespace identifier (MODULE_NAME)
must always be used.</t>
<t>The value of a metadata annotation SHALL be encoded in
exactly the same way as the value of a YANG leaf node having
the same type as the annotation, see <xref target="I-D.ietf-netmod-yang-json" pageno="false" format="default"/>, sec. 6.</t>
</section>
<section anchor="enc-cal" title="Adding Annotations to Anydata, Container and List Instances" toc="default">
<t>For an instance that is encoded as a JSON object (i.e., a
container, a list entry, or anydata node), the metadata
object is added as a new member of that object with the name
"@".</t>
<t>Examples:
<list style="symbols">
<t>"cask" is a container node:
<figure title="" suppress-title="false" align="left" alt="" width="" height="">
<artwork xml:space="preserve" name="" type="" align="left" alt="" width="" height="">
"cask": {
"@": {
"example-inactive:inactive": true
},
...
}</artwork>
</figure></t>
<t>"seq" is a list whose key is "name", annotation "inactive" is
added only to the first entry:
<figure title="" suppress-title="false" align="left" alt="" width="" height="">
<artwork xml:space="preserve" name="" type="" align="left" alt="" width="" height="">
"seq": [
{
"@": {
"example-inactive:inactive": true
},
"name": "one",
...
},
{
"name": "two",
...
}
]</artwork>
</figure></t>
</list></t>
</section>
<section anchor="enc-l" title="Adding Annotations to Anyxml and Leaf Instances" toc="default">
<t>For an anyxml or leaf instance, the metadata object is
added as a sibling name/value pair whose the name is the
symbol "@" concatenated with the name of the leaf or anyxml
member that is being annotated.</t>
<t>For example, if "flag" is a leaf node of the "boolean" type:
<figure title="" suppress-title="false" align="left" alt="" width="" height="">
<artwork xml:space="preserve" name="" type="" align="left" alt="" width="" height="">
"flag": true,
"@flag": {
"example-inactive:inactive": true
}</artwork>
</figure>
</t>
</section>
<section anchor="enc-ll" title="Adding Annotations to Leaf-list Instances" toc="default">
<t>For a leaf-list instance, which is represented as a JSON
array with values of a primitive type, annotations may be
assigned to one or more entries by adding a name/array pair
as a sibling of the leaf-list instance, where the name is
symbol "@" concatenated with the name of the leaf-list that
is being annotated, and the value is a JSON array whose i-th
element is the metadata object with annotations assigned to
the i-th entry of the leaf-list instance, or null if the
i-th entry has no annotations.</t>
<t>Trailing null values in that array, i.e., those following
the last non-null metadata object, MAY be omitted.</t>
<t>For example, in the following leaf-list instance with four
entries, the "inactive" annotation is added to the second and
third entry in the following way:
<figure title="" suppress-title="false" align="left" alt="" width="" height="">
<artwork xml:space="preserve" name="" type="" align="left" alt="" width="" height="">
"bibliomod:folio": [6, 3, 7, 8],
"@bibliomod:folio": [
null,
{"example-inactive:inactive": true},
{"example-inactive:inactive": true}
]</artwork>
</figure></t>
</section>
</section>
</section>
<section anchor="dsdl" title="Representing Annotations in DSDL Schemas" toc="default">
<t><xref target="RFC6110" pageno="false" format="default"/> defines the standard mapping of YANG
data models to Document Schema Definition Languages (DSDL) <xref target="ISO.19757-1" pageno="false" format="default"/>. This section specifies the mapping for
the extension statement "md:annotation" (<xref target="ietf-yang-metadata" pageno="false" format="default"/>), which enables validation of XML
instance documents containing metadata annotations.</t>
<t>The first step of the DSDL mapping procedure, i.e., the
transformation of the YANG data model to the hybrid schema (see
sec. 6 in <xref target="RFC6110" pageno="false" format="default"/>), is modified as follows:
<list style="numbers">
<t anchor="it.npdef">If the data model contains at least one
"md:annotation" statement, then a RELAX NG named pattern
definition MUST be added as a child of the root
<rng:grammar> element in the hybrid schema. It is
RECOMMENDED to use the name "__yang_metadata__" for this named
pattern.</t> <t anchor="it.npref">A reference to the named
pattern described in item <xref target="it.npdef" format="counter" pageno="false"/> MUST be included as a child of every
<rng:element> pattern that corresponds to a container,
leaf, list or leaf-list data node.</t>
<t>Every metadata annotation definition in the form
<figure title="" suppress-title="false" align="left" alt="" width="" height="">
<artwork xml:space="preserve" name="" type="" align="left" alt="" width="" height=""> md:annotation ARGUMENT;</artwork>
</figure>
or
<figure title="" suppress-title="false" align="left" alt="" width="" height="">
<artwork xml:space="preserve" name="" type="" align="left" alt="" width="" height="">
md:annotation ARGUMENT {
...
}</artwork>
</figure>
is mapped to the following RELAX NG pattern:
<figure title="" suppress-title="false" align="left" alt="" width="" height="">
<artwork xml:space="preserve" name="" type="" align="left" alt="" width="" height="">
<rng:attribute name="PREFIX:ARGUMENT">
...
</rng:attribute></artwork>
</figure>
where PREFIX is the namespace prefix bound to the namespace
URI of the YANG module that contains the "md:annotation"
statement. Each "rng:attribute" pattern SHALL be wrapped in
the <rng:optional> pattern, and this SHALL be inserted
as a child of the named pattern definition described in
item <xref target="it.npdef" format="counter" pageno="false"/>.</t>
<t>Substatements of "md:annotation", if there are any, SHALL
be mapped to children of the "rng:attribute" pattern exactly
as described in sec. 10 of <xref target="RFC6110" pageno="false" format="default"/>.</t>
</list></t>
<t>For example, the named pattern definition (item <xref target="it.npdef" format="counter" pageno="false"/>), when constructed only for
the "inactive" annotation, will have the following form:</t>
<figure title="" suppress-title="false" align="left" alt="" width="" height="">
<artwork xml:space="preserve" name="" type="" align="left" alt="" width="" height="">
<rng:define name="__yang_metadata__">
<rng:optional>
<rng:attribute name="ein:inactive">
<rng:choice>
<rng:value>true</rng:value>
<rng:value>false</rng:value>
</rng:choice>
</rng:attribute>
</rng:optional>
</rng:define></artwork>
</figure>
<t>Every "rng:element" pattern that corresponds to a container,
leaf, list or leaf-list data node will then contain a reference
to the above named pattern, for example</t>
<figure title="" suppress-title="false" align="left" alt="" width="" height="">
<artwork xml:space="preserve" name="" type="" align="left" alt="" width="" height="">
<rng:element name="foo:bar">
<rng:ref name="__yang_metadata__"/>
...
</rng:element></artwork>
</figure>
<t>Note that it is not necessary to use such a reference for
"rng:element" patterns corresponding to anyxml data nodes
because they already permit any XML attributes to be attached to
their instances.</t>
<t>The second step of the DSDL mapping procedure, i.e., the
transformation of the hybrid schema to RELAX NG, Schematron and
DSRL schemas, is unaffected by the inclusion of
"md:annotation".</t>
</section>
<section anchor="ietf-yang-metadata" title="Metadata YANG Module" toc="default">
<t>RFC Editor: In this section, replace all occurrences of 'XXXX'
with the actual RFC number and all occurrences of the revision date
below with the date of RFC publication (and remove this note).</t>
<figure title="" suppress-title="false" align="left" alt="" width="" height="">
<artwork xml:space="preserve" name="" type="" align="left" alt="" width="" height="">
<CODE BEGINS> file "ietf-yang-metadata@2015-06-09.yang"
module ietf-yang-metadata {
namespace "urn:ietf:params:xml:ns:yang:ietf-yang-metadata";
prefix "md";
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: Thomas Nadeau
<mailto:tnadeau@lucidvision.com>
WG Chair: Juergen Schoenwaelder
<mailto:j.schoenwaelder@jacobs-university.de>
Editor: Ladislav Lhotka
<mailto:lhotka@nic.cz>";
description
"This YANG module defines an extension statement that allows for
defining metadata annotations.
Copyright (c) 2014 IETF Trust and the persons identified as
authors of the code. All rights reserved.
Redistribution and use in source and binary forms, with or
without modification, is permitted pursuant to, and subject to
the license terms contained in, the Simplified BSD License set
forth in Section 4.c of the IETF Trust's Legal Provisions
Relating to IETF Documents
(http://trustee.ietf.org/license-info).
The key words 'MUST', 'MUST NOT', 'REQUIRED', 'SHALL', 'SHALL
NOT', 'SHOULD', 'SHOULD NOT', 'RECOMMENDED', 'MAY', and
'OPTIONAL' in the module text are to be interpreted as described
in RFC 2119 (http://tools.ietf.org/html/rfc2119).
This version of this YANG module is part of RFC XXXX
(http://tools.ietf.org/html/rfcXXXX); see the RFC itself for
full legal notices.";
revision 2015-06-09 {
description
"Initial revision.";
reference
"RFC XXXX: Defining and Using Metadata with YANG";
}
extension annotation {
argument name;
description
"This extension allows for defining metadata annotations in
YANG modules. The 'md:annotation' statement can appear only at
the top level of a YANG module.
An annotation defined with this extension statement inherits
the namespace and other context from the YANG module in which
it is defined.
Other properties of the annotation and documentation are
specified using the following standard YANG substatements (all
are optional): 'description', 'if-feature', 'reference',
'status', 'type' and 'units'. If the 'type' statement is not
present, the built-in 'string' type is used by default.
A server announces syntactic support for a particular
annotation by including the module in which the annotation is
defined among the advertised YANG modules (e.g., in NETCONF
hello message).
Semantics and usage rules for an annotation MUST be specified
separately. The 'description' and/or 'reference' statements
SHOULD provide corresponding links.
XML and JSON encoding of annotations is defined in
RFC XXXX.";
}
}
<CODE ENDS></artwork>
</figure>
</section>
<section anchor="iana" title="IANA Considerations" toc="default">
<t>RFC Editor: In this section, replace all occurrences of 'XXXX'
with the actual RFC number and all occurrences of the revision date
below with the date of RFC publication (and remove this note).</t>
<t>This document registers the following namespace URI in the
IETF XML registry <xref target="RFC3688" pageno="false" format="default"/>:</t>
<figure title="" suppress-title="false" align="left" alt="" width="" height="">
<artwork xml:space="preserve" name="" type="" align="left" alt="" width="" height="">
---------------------------------------------------------------------
URI: urn:ietf:params:xml:ns:yang:ietf-yang-metadata
Registrant Contact: The IESG.
XML: N/A, the requested URI is an XML namespace.
---------------------------------------------------------------------
</artwork>
</figure>
<t>This document registers the following YANG module in the YANG
Module Names registry <xref target="I-D.ietf-netmod-rfc6020bis" pageno="false" format="default"/>:</t>
<figure title="" suppress-title="false" align="left" alt="" width="" height="">
<artwork xml:space="preserve" name="" type="" align="left" alt="" width="" height="">
---------------------------------------------------------------------
name: ietf-yang-metadata
namespace: urn:ietf:params:xml:ns:yang:ietf-yang-metadata
prefix: md
reference: RFC XXXX
---------------------------------------------------------------------
</artwork>
</figure>
</section>
<section anchor="security" title="Security Considerations" toc="default">
<t>This document introduces a mechanism for defining the syntax
of metadata annotations in YANG modules and using them with
instances of YANG data nodes. By itself, this mechanism
represents no security threat. Security implications of a
particular annotation defined using this mechanism have to be
duly considered and documented in the specification of the
annotation's semantics.</t>
</section>
<section anchor="sec.ack" title="Acknowledgments" toc="default">
<t>The author wishes to thank Andy Bierman, Martin Bjorklund and
Kent Watsen for their helpful comments and suggestions.</t>
</section>
</middle>
<back>
<references title="Normative References">
<reference anchor="I-D.ietf-netmod-rfc6020bis">
<front>
<title>YANG - A Data Modeling Language for the Network Configuration Protocol (NETCONF)</title>
<author initials="M" surname="Bjorklund" fullname="Martin Bjorklund">
<organization/>
</author>
<date month="May" day="4" year="2015"/>
<abstract><t>YANG is a data modeling language used to model configuration and state data manipulated by the Network Configuration Protocol (NETCONF), NETCONF remote procedure calls, and NETCONF notifications. This document obsoletes RFC 6020.</t></abstract>
</front>
<seriesInfo name="Internet-Draft" value="draft-ietf-netmod-rfc6020bis-05"/>
<format type="TXT" target="http://www.ietf.org/internet-drafts/draft-ietf-netmod-rfc6020bis-05.txt"/>
</reference>
<reference anchor="I-D.ietf-netmod-yang-json">
<front>
<title>JSON Encoding of Data Modeled with YANG</title>
<author initials="L" surname="Lhotka" fullname="Ladislav Lhotka">
<organization/>
</author>
<date month="February" day="24" year="2015"/>
<abstract><t>This document defines encoding rules for representing configuration, state data, RPC input and output parameters, and notifications defined using YANG as JavaScript Object Notation (JSON) text.</t></abstract>
</front>
<seriesInfo name="Internet-Draft" value="draft-ietf-netmod-yang-json-03"/>
<format type="TXT" target="http://www.ietf.org/internet-drafts/draft-ietf-netmod-yang-json-03.txt"/>
</reference>
<reference anchor="RFC2119">
<front>
<title abbrev="RFC Key Words">Key words for use in RFCs to Indicate Requirement Levels</title>
<author initials="S." surname="Bradner" fullname="Scott Bradner">
<organization>Harvard University</organization>
<address>
<postal>
<street>1350 Mass. Ave.</street>
<street>Cambridge</street>
<street>MA 02138</street></postal>
<phone>- +1 617 495 3864</phone>
<email>sob@harvard.edu</email></address></author>
<date year="1997" month="March"/>
<area>General</area>
<keyword>keyword</keyword>
<abstract>
<t>
In many standards track documents several words are used to signify
the requirements in the specification. These words are often
capitalized. This document defines these words as they should be
interpreted in IETF documents. Authors who follow these guidelines
should incorporate this phrase near the beginning of their document:
<list>
<t>
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.
</t></list></t>
<t>
Note that the force of these words is modified by the requirement
level of the document in which they are used.
</t></abstract></front>
<seriesInfo name="BCP" value="14"/>
<seriesInfo name="RFC" value="2119"/>
<format type="TXT" octets="4723" target="http://www.rfc-editor.org/rfc/rfc2119.txt"/>
<format type="HTML" octets="17970" target="http://xml.resource.org/public/rfc/html/rfc2119.html"/>
<format type="XML" octets="5777" target="http://xml.resource.org/public/rfc/xml/rfc2119.xml"/>
</reference>
<reference anchor="RFC3688">
<front>
<title>The IETF XML Registry</title>
<author initials="M." surname="Mealling" fullname="M. Mealling">
<organization/></author>
<date year="2004" month="January"/>
<abstract>
<t>This document describes an IANA maintained registry for IETF standards which use Extensible Markup Language (XML) related items such as Namespaces, Document Type Declarations (DTDs), Schemas, and Resource Description Framework (RDF) Schemas.</t></abstract></front>
<seriesInfo name="BCP" value="81"/>
<seriesInfo name="RFC" value="3688"/>
<format type="TXT" octets="17325" target="http://www.rfc-editor.org/rfc/rfc3688.txt"/>
</reference>
<reference anchor="RFC6110">
<front>
<title>Mapping YANG to Document Schema Definition Languages and Validating NETCONF Content</title>
<author initials="L." surname="Lhotka" fullname="L. Lhotka">
<organization/></author>
<date year="2011" month="February"/>
<abstract>
<t>This document specifies the mapping rules for translating YANG data models into Document Schema Definition Languages (DSDL), a coordinated set of XML schema languages standardized as ISO/IEC 19757. The following DSDL schema languages are addressed by the mapping: Regular Language for XML Next Generation (RELAX NG), Schematron, and Schematron and Document Schema Renaming Language (DSRL). The mapping takes one or more YANG modules and produces a set of DSDL schemas for a selected target document type -- datastore content, Network Configuration Protocol (NETCONF) messages, etc. Procedures for schema-based validation of such documents are also discussed. [STANDARDS-TRACK]</t></abstract></front>
<seriesInfo name="RFC" value="6110"/>
<format type="TXT" octets="192547" target="http://www.rfc-editor.org/rfc/rfc6110.txt"/>
</reference>
<reference anchor="RFC6241">
<front>
<title>Network Configuration Protocol (NETCONF)</title>
<author initials="R." surname="Enns" fullname="R. Enns">
<organization/></author>
<author initials="M." surname="Bjorklund" fullname="M. Bjorklund">
<organization/></author>
<author initials="J." surname="Schoenwaelder" fullname="J. Schoenwaelder">
<organization/></author>
<author initials="A." surname="Bierman" fullname="A. Bierman">
<organization/></author>
<date year="2011" month="June"/>
<abstract>
<t>The Network Configuration Protocol (NETCONF) defined in this document provides mechanisms to install, manipulate, and delete the configuration of network devices. It uses an Extensible Markup Language (XML)-based data encoding for the configuration data as well as the protocol messages. The NETCONF protocol operations are realized as remote procedure calls (RPCs). This document obsoletes RFC 4741. [STANDARDS-TRACK]</t></abstract></front>
<seriesInfo name="RFC" value="6241"/>
<format type="TXT" octets="209465" target="http://www.rfc-editor.org/rfc/rfc6241.txt"/>
</reference>
<reference anchor="RFC7159">
<front>
<title>The JavaScript Object Notation (JSON) Data Interchange Format</title>
<author initials="T." surname="Bray" fullname="T. Bray">
<organization/></author>
<date year="2014" month="March"/>
<abstract>
<t>JavaScript Object Notation (JSON) is a lightweight, text-based, language-independent data interchange format. It was derived from the ECMAScript Programming Language Standard. JSON defines a small set of formatting rules for the portable representation of structured data.</t><t> This document removes inconsistencies with other specifications of JSON, repairs specification errors, and offers experience-based interoperability guidance.</t></abstract></front>
<seriesInfo name="RFC" value="7159"/>
<format type="TXT" octets="27451" target="http://www.rfc-editor.org/rfc/rfc7159.txt"/>
</reference>
<reference anchor="W3C.REC-xml-infoset-20040204" target="http://www.w3.org/TR/2004/REC-xml-infoset-20040204">
<front>
<title>XML Information Set (Second Edition)</title>
<author initials="J." surname="Cowan" fullname="John Cowan">
<organization/>
</author>
<author initials="R." surname="Tobin" fullname="Richard Tobin">
<organization/>
</author>
<date month="February" day="4" year="2004"/>
</front>
<seriesInfo name="World Wide Web Consortium Recommendation" value="REC-xml-infoset-20040204"/>
<format type="HTML" target="http://www.w3.org/TR/2004/REC-xml-infoset-20040204"/>
</reference>
</references>
<references title="Informative References">
<reference anchor="ISO.19757-1">
<front>
<title>
Document Schema Definition Languages (DSDL) - Part 1: Overview
</title>
<author>
<organization>International Organization for Standardization</organization>
</author>
<date day="14" month="November" year="2004"/>
</front>
<seriesInfo name="ISO/IEC" value="19757-1"/>
<format type="PDF" target="http://www.dsdl.org/0567.pdf"/>
</reference>
<reference anchor="I-D.ietf-netconf-restconf">
<front>
<title>RESTCONF Protocol</title>
<author initials="A" surname="Bierman" fullname="Andy Bierman">
<organization/>
</author>
<author initials="M" surname="Bjorklund" fullname="Martin Bjorklund">
<organization/>
</author>
<author initials="K" surname="Watsen" fullname="Kent Watsen">
<organization/>
</author>
<date month="June" day="4" year="2015"/>
<abstract><t>This document describes an HTTP-based protocol that provides a programmatic interface for accessing data defined in YANG, using the datastores defined in NETCONF.</t></abstract>
</front>
<seriesInfo name="Internet-Draft" value="draft-ietf-netconf-restconf-05"/>
<format type="TXT" target="http://www.ietf.org/internet-drafts/draft-ietf-netconf-restconf-05.txt"/>
</reference>
</references>
<section title="Change Log" toc="default">
<t>RFC Editor: Remove this section upon publication as an RFC.</t>
<section title="Changes Between Revisions -00 and -01" toc="default">
<t>
<list style="symbols">
<t>Define JSON encoding for annotations attached to 'anydata' nodes.</t>
</list>
</t>
</section>
<section title="Changes Between draft-lhotka-netmod-yang-metadata-01 and draft-ietf-netmod-yang-metadata-00" toc="default">
<t>
<list style="symbols">
<t>References to RFC 6020 were changed to the 6021bis
I-D.</t>
<t>Text about RFC 2119 key words was added to
"ietf-yang-metadata" module description.</t>
</list>
</t>
</section>
<section title="Changes Between draft-lhotka-netmod-yang-metadata-00 and -01" toc="default">
<t>
<list style="symbols">
<t>Encoding of annotations for anyxml nodes was changed to
be the same as for leafs. This was necessary because
anyxml value now needn't be an object.</t>
<t>It is stated that "md:annotation" statement defines
only the syntax of an annotation.</t>
<t>Allowed "if-feature" as a substatement of
"md:annotation".</t>
</list>
</t>
</section>
</section>
</back>
</rfc>
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