draft-ietf-netmod-yang-metadata-07.txt   rfc7952.txt 
NETMOD Working Group L. Lhotka Internet Engineering Task Force (IETF) L. Lhotka
Internet-Draft CZ.NIC Request for Comments: 7952 CZ.NIC
Updates: 6110 (if approved) March 21, 2016 Updates: 6110 August 2016
Intended status: Standards Track Category: Standards Track
Expires: September 22, 2016 ISSN: 2070-1721
Defining and Using Metadata with YANG Defining and Using Metadata with YANG
draft-ietf-netmod-yang-metadata-07
Abstract Abstract
This document defines a YANG extension statement that allows for This document defines a YANG extension that allows for defining
defining metadata annotations in YANG modules. The document also metadata annotations in YANG modules. The document also specifies
specifies XML and JSON encoding of annotations and other rules for XML and JSON encoding of annotations and other rules for annotating
annotating instances of YANG data nodes. instances of YANG data nodes.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This is an Internet Standards Track document.
provisions of BCP 78 and BCP 79.
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and how to provide feedback on it may be obtained at
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5
2.1. Keywords . . . . . . . . . . . . . . . . . . . . . . . . 5 2.1. Key Words . . . . . . . . . . . . . . . . . . . . . . . . 5
2.2. Terms Defined in Other Documents . . . . . . . . . . . . 5 2.2. Terms Defined in Other Documents . . . . . . . . . . . . 5
2.3. Namespaces and Prefixes . . . . . . . . . . . . . . . . . 6 2.3. Namespaces and Prefixes . . . . . . . . . . . . . . . . . 7
2.4. Definitions of New Terms . . . . . . . . . . . . . . . . 7 2.4. Definitions of New Terms . . . . . . . . . . . . . . . . 7
3. Defining Annotations in YANG . . . . . . . . . . . . . . . . 7 3. Defining Annotations in YANG . . . . . . . . . . . . . . . . 8
3.1. Example Definition . . . . . . . . . . . . . . . . . . . 8 3.1. Example Definition . . . . . . . . . . . . . . . . . . . 9
4. Using Annotations . . . . . . . . . . . . . . . . . . . . . . 8 4. Using Annotations . . . . . . . . . . . . . . . . . . . . . . 9
5. The Encoding of Annotations . . . . . . . . . . . . . . . . . 9 5. The Encoding of Annotations . . . . . . . . . . . . . . . . . 10
5.1. XML Encoding . . . . . . . . . . . . . . . . . . . . . . 9 5.1. XML Encoding . . . . . . . . . . . . . . . . . . . . . . 10
5.2. JSON Encoding . . . . . . . . . . . . . . . . . . . . . . 10 5.2. JSON Encoding . . . . . . . . . . . . . . . . . . . . . . 11
5.2.1. Metadata Object and Annotations . . . . . . . . . . . 10 5.2.1. Metadata Object and Annotations . . . . . . . . . . . 11
5.2.2. Adding Annotations to Anydata, Container and List 5.2.2. Adding Annotations to anydata, container, and list
Entries . . . . . . . . . . . . . . . . . . . . . . . 11 Entries . . . . . . . . . . . . . . . . . . . . . . . 12
5.2.3. Adding Annotations to Anyxml and Leaf Instances . . . 11 5.2.3. Adding Annotations to anyxml and leaf Instances . . . 12
5.2.4. Adding Annotations to Leaf-list Entries . . . . . . . 12 5.2.4. Adding Annotations to leaf-list Entries . . . . . . . 13
6. Representing Annotations in DSDL Schemas . . . . . . . . . . 13 6. Representing Annotations in DSDL Schemas . . . . . . . . . . 14
7. Metadata YANG Module . . . . . . . . . . . . . . . . . . . . 14 7. Metadata YANG Module . . . . . . . . . . . . . . . . . . . . 16
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 18
9. Security Considerations . . . . . . . . . . . . . . . . . . . 17 9. Security Considerations . . . . . . . . . . . . . . . . . . . 18
10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 17 10. References . . . . . . . . . . . . . . . . . . . . . . . . . 19
11. References . . . . . . . . . . . . . . . . . . . . . . . . . 17 10.1. Normative References . . . . . . . . . . . . . . . . . . 19
11.1. Normative References . . . . . . . . . . . . . . . . . . 17 10.2. Informative References . . . . . . . . . . . . . . . . . 20
11.2. Informative References . . . . . . . . . . . . . . . . . 18 Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 21
Appendix A. Change Log . . . . . . . . . . . . . . . . . . . . . 19 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 21
A.1. Changes Between Revisions -06 and -07 . . . . . . . . . . 19
A.2. Changes Between Revisions -05 and -06 . . . . . . . . . . 19
A.3. Changes Between Revisions -04 and -05 . . . . . . . . . . 19
A.4. Changes Between Revisions -03 and -04 . . . . . . . . . . 19
A.5. Changes Between Revisions -02 and -03 . . . . . . . . . . 19
A.6. Changes Between Revisions -01 and -02 . . . . . . . . . . 19
A.7. Changes Between Revisions -00 and -01 . . . . . . . . . . 20
A.8. Changes Between draft-lhotka-netmod-yang-metadata-01 and
draft-ietf-netmod-yang-metadata-00 . . . . . . . . . . . 20
A.9. Changes Between draft-lhotka-netmod-yang-metadata-00 and
-01 . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 20
1. Introduction 1. Introduction
There is a need to be able to annotate instances of There is a need to be able to annotate instances of YANG [RFC7950]
YANG [I-D.ietf-netmod-rfc6020bis] data nodes with metadata. Typical data nodes with metadata. Typical use cases are as follows:
use cases are:
o Complementing regular data model information with instance- o Complementing regular data model information with
specific metadata, comments etc. instance-specific metadata, comments, etc.
o Providing information about data rendering in user interfaces. o Providing information about the rendering of data in user
interfaces.
o Deactivating a subtree in a configuration datastore while keeping o Deactivating a subtree in a configuration datastore while keeping
the data in place. the data in place.
o Network management protocols often use metadata annotations for o Network management protocols often use metadata annotations for
various purposes in both operation requests and responses. For various purposes in both operation requests and responses. For
example, the <edit-config> operation in the NETCONF protocol (see example, the <edit-config> operation in the Network Configuration
section 7.2 of [RFC6241]) uses annotations in the form of XML Protocol (NETCONF) (see Section 7.2 of [RFC6241]) uses annotations
attributes for identifying the location in a configuration in the form of XML attributes for identifying the location in a
datastore and the type of the operation. configuration datastore and the type of the operation.
However, metadata annotations could potentially lead to However, metadata annotations could potentially lead to
interoperability problems if they are used in an ad hoc fashion by interoperability problems if they are used in an ad hoc fashion by
different parties and/or without proper documentation. A sound different parties and/or without proper documentation. A sound
metadata framework for YANG should therefore satisfy these metadata framework for YANG should therefore satisfy these
requirements: requirements:
1. The set of annotations must be extensible in a decentralised 1. The set of annotations must be extensible in a decentralized
manner so as to allow for defining new annotations without manner so as to allow for defining new annotations without
running into the risk of collisions with annotations defined and running the risk of collisions with annotations defined and used
used by others. by others.
2. Syntax and semantics of annotations must be documented and the 2. The syntax and semantics of annotations must be documented, and
documentation must be easily accessible. the documentation must be easily accessible.
3. Clients of network management protocols such as NETCONF [RFC6241] 3. Clients of network management protocols such as NETCONF [RFC6241]
or RESTCONF [I-D.ietf-netconf-restconf] must be able to discover or RESTCONF [RESTCONF] must be able to discover all annotations
all annotations supported by a given server and identify each of supported by a given server and identify each of them correctly.
them correctly.
4. Annotations sent by a server should not break clients that don't 4. Annotations sent by a server should not break clients that don't
support them. support them.
This document proposes a systematic way for defining metadata This document proposes a systematic way to define metadata
annotations. For this purpose, YANG extension statement "annotation" annotations. For this purpose, the YANG extension "annotation" is
is defined in the module "ietf-yang-metadata" (Section 7). Other defined in the module "ietf-yang-metadata" (Section 7). Other YANG
YANG modules importing this module can use the "annotation" statement modules importing this module can use the "annotation" statement for
for defining one or more annotations. defining one or more annotations.
The benefits of defining the metadata annotations in a YANG module The benefits of defining the metadata annotations in a YANG module
are the following: are the following:
o Each annotation is bound to a YANG module name and namespace URI. o Each annotation is bound to a YANG module name and namespace URI.
This makes its encoding in instance documents (both XML and JSON) This makes its encoding in instance documents (both XML and JSON)
straightforward and consistent with the encoding of YANG data node straightforward and consistent with the encoding of YANG data node
instances. instances.
o Annotations defined in IETF standard-track documents are o Annotations defined in IETF Standards Track documents are
indirectly registered through IANA in the "YANG Module Names" indirectly registered through IANA in the "YANG Module Names"
registry [RFC6020]. registry [RFC6020].
o Annotations are included in the data model. YANG compilers and o Annotations are included in the data model. YANG compilers and
tools supporting a certain annotation can thus take them into tools supporting a certain annotation can thus take them into
account and modify their behavior accordingly. account and modify their behavior accordingly.
o Semantics of an annotation are defined in the "description" and o The semantics of an annotation are defined in the "description"
"reference" statements. and "reference" statements.
o An annotation can be declared as conditional by using the "if- o An annotation can be declared as conditional by using the
feature" statement. "if-feature" statement.
o The type of each annotation is explicitly specified; any YANG o The type of each annotation is explicitly specified; any YANG
built-in or derived type that is available for leaf or leaf-list built-in or derived type that is available for leaf or leaf-list
data nodes may be specified for annotations as well. data nodes may be specified for annotations as well.
In the XML encoding, XML attributes are a natural instrument for In the XML encoding, XML attributes are a natural instrument for
attaching annotations to data node instances. This document attaching annotations to data node instances. This document
deliberately adopts some restrictions in order to remain compatible deliberately adopts some restrictions in order to remain compatible
with the XML encoding of YANG data node instances and limitations of with the XML encoding of YANG data node instances and limitations of
XML attributes. Specifically, XML attributes. Specifically,
o annotations can only be scalar values; o annotations can only be scalar values.
o annotations cannot be attached to a whole list or leaf-list o annotations cannot be attached to a whole list or leaf-list
instance, only to individual list or leaf-list entries. instance, only to individual list or leaf-list entries.
Due to the rules for YANG extensions (see sec. 6.3.1 in Due to the rules for YANG extensions (see Section 6.3.1 in
[I-D.ietf-netmod-rfc6020bis]), annotation definitions posit [RFC7950]), annotation definitions posit relatively weak conformance
relatively weak conformance requirements. The alternative of requirements. The alternative of introducing a new built-in YANG
introducing a new built-in YANG statement for defining annotations statement for defining annotations was considered, but it was seen as
was considered, but it was seen as a major change to the language a major change to the language that is inappropriate for YANG 1.1,
that is inappropriate for YANG 1.1, which was chartered as a which was chartered as a maintenance revision. After evaluating
maintenance revision. After evaluating real-life usage of metadata real-life usage of metadata annotations, it is conceivable that such
annotations, it is conceivable that such a new built-in statement a new built-in statement might be added in a future revision of YANG.
might be added in a future revision of YANG.
2. Terminology 2. Terminology
2.1. Keywords
2.1. Key Words
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119]. document are to be interpreted as described in [RFC2119].
2.2. Terms Defined in Other Documents 2.2. Terms Defined in Other Documents
The following terms are defined in [RFC6241]: The following terms are defined in [RFC6241]:
o capability, o capability
o client, o client
o datastore, o datastore
o message, o message
o protocol operation, o protocol operation
o server. o server
The following terms are defined in [I-D.ietf-netmod-rfc6020bis]: The following terms are defined in [RFC7950]:
o action, o action
o anydata, o anydata
o anyxml, o anyxml
o built-in type, o built-in type
o container, o container
o data model, o data model
o data node, o data node
o data tree, o data tree
o derived type, o derived type
o extension, o extension
o leaf, o leaf
o leaf-list
o leaf-list, o list
o list,
o module, o module
o RPC input and output. o Remote Procedure Call (RPC) input and output
The following terms are defined in [W3C.REC-xml-infoset-20040204]: The following terms are defined in [XML-INFOSET]:
o attribute, o attribute
o document, o document
o element. o element
The following terms are defined in [W3C.REC-xml-names11-20060816]: The following terms are defined in [XML-NAMES]:
o local name, o local name
o namespace name, o namespace name
o prefix, o prefix
o qualified name. o qualified name
The following terms are defined in [RFC7159]: The following terms are defined in [RFC7159]:
o array, o array
o member, o member
o object, o object
o primitive type. o primitive type
2.3. Namespaces and Prefixes 2.3. Namespaces and Prefixes
In the following text, XML element names and YANG extension In the following text, XML element names and YANG extension
statements are always written with explicit namespace prefixes that statements are always written with explicit namespace prefixes that
are assumed to be bound to URI references as shown in Table 1. are assumed to be bound to URI references as shown in Table 1.
+--------+------------------------------------------------+ +--------+------------------------------------------------+
| Prefix | URI Reference | | Prefix | URI Reference |
+--------+------------------------------------------------+ +--------+------------------------------------------------+
| elm | http://example.org/example-last-modified | | elm | http://example.org/example-last-modified |
| md | urn:ietf:params:xml:ns:yang:ietf-yang-metadata | | md | urn:ietf:params:xml:ns:yang:ietf-yang-metadata |
| rng | http://relaxng.org/ns/structure/1.0 | | rng | http://relaxng.org/ns/structure/1.0 |
+--------+------------------------------------------------+ +--------+------------------------------------------------+
Table 1: Used namespace prefixes and corresponding URI references Table 1: Used Namespace Prefixes and Corresponding URI References
2.4. Definitions of New Terms 2.4. Definitions of New Terms
o annotation: a single item of metadata that is attached to YANG o annotation: a single item of metadata that is attached to YANG
data node instances. data node instances.
o metadata: additional information that complements a data tree. o metadata: additional information that complements a data tree.
o metadata object: an object in JSON encoding that contains all o metadata object: an object in JSON encoding that contains all
annotations attached to a given data node instance. annotations attached to a given data node instance.
3. Defining Annotations in YANG 3. Defining Annotations in YANG
Metadata annotations are defined by YANG extension statement Metadata annotations are defined by the YANG extension
"md:annotation". This YANG language extension is defined in the "md:annotation". This YANG language extension is defined in the
module "ietf-yang-metadata" (Section 7). module "ietf-yang-metadata" (Section 7).
Substatements of "md:annotation" are shown in Table 2. They are all Substatements of "md:annotation" are shown in Table 2. They are all
core YANG statements, and the numbers in the second column refer to core YANG statements, and the numbers in the second column refer to
the corresponding section in [I-D.ietf-netmod-rfc6020bis] where each the corresponding section in [RFC7950] where each statement is
statement is described. described.
+--------------+---------------------+-------------+ +--------------+---------------------+-------------+
| substatement | RFC 6020bis section | cardinality | | substatement | section in RFC 7950 | cardinality |
+--------------+---------------------+-------------+ +--------------+---------------------+-------------+
| description | 7.21.3 | 0..1 | | description | 7.21.3 | 0..1 |
| if-feature | 7.20.2 | 0..n | | if-feature | 7.20.2 | 0..n |
| reference | 7.21.4 | 0..1 | | reference | 7.21.4 | 0..1 |
| status | 7.21.2 | 0..1 | | status | 7.21.2 | 0..1 |
| type | 7.6.3 | 1 | | type | 7.6.3 | 1 |
| units | 7.3.3 | 0..1 | | units | 7.3.3 | 0..1 |
+--------------+---------------------+-------------+ +--------------+---------------------+-------------+
Table 2: Substatements of "md:annotation". Table 2: Substatements of "md:annotation"
An annotation carries a single value. The type substatement, which An annotation carries a single value. The "type" substatement, which
MUST be present, takes as an argument the name of an existing built- MUST be present, takes as an argument the name of an existing
in or derived type, and the value of the annotation MUST match this built-in or derived type, and the value of the annotation MUST match
type. See Section 7.4 of [I-D.ietf-netmod-rfc6020bis] for details. this type. See Section 7.4 of [RFC7950] for details.
An annotation can be made conditional by using one or more "if- An annotation can be made conditional by using one or more
feature" statements; the annotation is then supported only by servers "if-feature" statements; the annotation is then supported only by
that advertise the corresponding feature. servers that advertise the corresponding feature.
The semantics and usage rules for an annotation SHOULD be fully The semantics and usage rules for an annotation SHOULD be fully
specified in "description", "reference" and "units" statements. specified in "description", "reference", and "units" statements.
An annotation MUST NOT change the data tree semantics defined by An annotation MUST NOT change the data tree semantics defined by
YANG. For example, it is illegal to define and use an annotation YANG. For example, it is illegal to define and use an annotation
that allows for overriding uniqueness of leaf-list entries. that allows for overriding uniqueness of leaf-list entries.
The "status" statement can be used exactly as for YANG data nodes. The "status" statement can be used exactly as it is used for YANG
data nodes.
A YANG module containing one or more "md:annotation" extension A YANG module containing one or more "md:annotation" statements
statements SHOULD NOT be used for defining data nodes or groupings. SHOULD NOT be used for defining data nodes or groupings. Also,
Also, derived types, identities and features SHOULD NOT be defined in derived types, identities, and features SHOULD NOT be defined in such
such a module unless they are used by the definitions of annotations a module unless they are used by the definitions of annotations in
in that module. that module.
3.1. Example Definition 3.1. Example Definition
The following module defines the "last-modified" annotation: The following module defines the "last-modified" annotation:
module example-last-modified { module example-last-modified {
namespace "http://example.org/example-last-modified"; namespace "http://example.org/example-last-modified";
prefix "elm"; prefix "elm";
import ietf-yang-types { import ietf-yang-types {
prefix "yang"; prefix "yang";
} }
import ietf-yang-metadata { import ietf-yang-metadata {
prefix "md"; prefix "md";
} }
md:annotation last-modified { md:annotation last-modified {
type yang:date-and-time; type yang:date-and-time;
description description
"This annotation contains date and time when the "This annotation contains the date and time when the
annotated instance was last modified (or created)."; annotated instance was last modified (or created).";
} }
} }
4. Using Annotations 4. Using Annotations
By advertising a YANG module in which a metadata annotation is By advertising a YANG module in which a metadata annotation is
defined using the "md:annotation" statement, a server indicates that defined using the "md:annotation" statement, a server indicates that
it is prepared to handle that annotation according to the it is prepared to handle that annotation according to the
annotation's definition. That is, an annotation advertised by the annotation's definition. That is, an annotation advertised by the
server may be attached to an instance of a data node defined in any server may be attached to an instance of a data node defined in any
YANG module that is implemented by the server. YANG module that is implemented by the server.
Depending on its semantics, an annotation may have an effect only in Depending on its semantics, an annotation may have an effect only in
certain data trees and/or on instances of specific data nodes types. certain data trees and/or on instances of specific types of data
nodes.
A client MUST NOT add a specific annotation to data node instances if A client MUST NOT add a specific annotation to data node instances if
the server didn't advertise it. the server didn't advertise it.
Due care has to be exercised when introducing annotations in network Due care has to be exercised when introducing annotations in network
management systems in order to avoid interoperability problems and management systems in order to avoid interoperability problems and
software failures caused by a client that does not understand the software failures caused by a client that does not understand the
annotations' semantics. Generally, it is safe for a server to use annotations' semantics. Generally, it is safe for a server to use
annotations in the following cases: annotations in the following cases:
o An annotation is an integral part of a built-in or negotiated o An annotation is an integral part of a built-in or negotiated
protocol capability. protocol capability.
o An annotation contains auxiliary information that is not critical o An annotation contains auxiliary information that is not critical
for protocol operation. for protocol operation.
o The client explicitly asks the server, e.g., via a parameter of a o The client explicitly asks the server, e.g., via a parameter of a
protocol operation request, for including an annotation in the protocol operation request, to include an annotation in the
response. response.
5. The Encoding of Annotations 5. The Encoding of Annotations
XML attributes are a natural choice for encoding metadata in XML XML attributes are a natural choice for encoding metadata in XML
instance documents. For JSON [RFC7159], there is no generally instance documents. For JSON [RFC7159], there is no generally
established method for encoding metadata. This document thus established method for encoding metadata. This document thus
introduces a special encoding method that is consistent with the JSON introduces a special encoding method that is consistent with the JSON
encoding of YANG data node instances as defined encoding of YANG data node instances as defined in [RFC7951].
in [I-D.ietf-netmod-yang-json].
5.1. XML Encoding 5.1. XML Encoding
Metadata annotations are added to XML-encoded instances of YANG data Metadata annotations are added to XML-encoded instances of YANG data
nodes as XML attributes according to these rules: nodes as XML attributes according to these rules:
o The local name of the attribute SHALL be the same as the name of o The local name of the attribute SHALL be the same as the name of
the annotation specified in the argument of the corresponding the annotation specified in the argument of the corresponding
"md:annotation" statement. "md:annotation" statement.
o The namespace of the attribute SHALL be identified by the URI that o The namespace of the attribute SHALL be identified by the URI that
appears as the argument of the "namespace" statement in the YANG appears as the argument of the "namespace" statement in the YANG
module where the annotation is defined. It is RECOMMENDED that module where the annotation is defined. It is RECOMMENDED that
the prefix specified by the "prefix" statement in the same module the prefix specified by the "prefix" statement in the same module
is used in the qualified name of the attribute. be used in the qualified name of the attribute.
o The attribute value SHALL be encoded in the same way as the value o The attribute value SHALL be encoded in the same way as the value
of a YANG leaf instance having the same type, of a YANG leaf instance having the same type; see Section 9 of
see [I-D.ietf-netmod-rfc6020bis], sec. 9. [RFC7950].
For example, the "last-modified" annotation defined in Section 3.1 For example, the "last-modified" annotation defined in Section 3.1
may be encoded as follows: may be encoded as follows:
<foo xmlns:elm="http://example.org/example-last-modified" <foo xmlns:elm="http://example.org/example-last-modified"
elm:last-modified="2015-09-16T10:27:35+02:00"> elm:last-modified="2015-09-16T10:27:35+02:00">
... ...
</foo> </foo>
5.2. JSON Encoding 5.2. JSON Encoding
The JSON metadata encoding defined in this section has the following The JSON metadata encoding defined in this section has the following
properties: properties:
1. The encoding of YANG data node instances as defined in 1. The encoding of YANG data node instances as defined in [RFC7951]
[I-D.ietf-netmod-yang-json] does not change. does not change.
2. Namespaces of metadata annotations are encoded in the same way as 2. Namespaces of metadata annotations are encoded in the same way as
namespaces of YANG data node instances, see namespaces of YANG data node instances; see [RFC7951].
[I-D.ietf-netmod-yang-json].
5.2.1. Metadata Object and Annotations 5.2.1. Metadata Object and Annotations
All metadata annotations assigned to a YANG data node instance are All metadata annotations assigned to a YANG data node instance are
encoded as members (name/value pairs) of a single JSON object, encoded as members (name/value pairs) of a single JSON object,
henceforth denoted as the metadata object. The placement and name of 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 this object depend on the type of the data node as specified in the
following subsections. following subsections.
The name of a metadata annotation (as a member of the metadata The name of a metadata annotation (as a member of the metadata
object) has the following ABNF syntax [RFC5234], where the production object) has the following ABNF syntax [RFC5234], where the production
for "identifier" is defined in sec. 13 of for "identifier" is defined in Section 14 of [RFC7950]:
[I-D.ietf-netmod-rfc6020bis]
annotation-name = identifier ":" identifier annotation-name = identifier ":" identifier
where the left identifier is the name of the YANG module in which the where the left identifier is the name of the YANG module in which the
annotation is defined, and the identifier on the right is the name of annotation is defined and the identifier on the right is the name of
the annotation specified in the argument of the corresponding the annotation specified in the argument of the corresponding
"md:annotation" statement. "md:annotation" statement.
Note that unlike member names of YANG data node instances in JSON Note that unlike member names of YANG data node instances in JSON
encoding (see sec. 4 in [I-D.ietf-netmod-yang-json]), for annotations encoding (see Section 4 in [RFC7951]), for annotations the explicit
the explicit namespace identifier (module name) must always be namespace identifier (module name) must always be present.
present.
The value of a metadata annotation SHALL be encoded in exactly the 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 same way as the value of a YANG leaf node having the same type as the
annotation, see [I-D.ietf-netmod-yang-json], sec. 6. annotation; see Section 6 of [RFC7951].
5.2.2. Adding Annotations to Anydata, Container and List Entries 5.2.2. Adding Annotations to anydata, container, and list Entries
For a data node instance that is encoded as a JSON object (i.e., a For a data node instance that is encoded as a JSON object (i.e., a
container, list entry, or anydata node), the metadata object is added container, list entry, or anydata node), the metadata object is added
as a new member of that object with the name "@". as a new member of that object with the name "@".
Examples: Examples:
o "cask" is a container or anydata node: o "cask" is a container or anydata node:
"cask": { "cask": {
"@": { "@": {
"example-last-modified:last-modified": "example-last-modified:last-modified":
"2015-09-16T10:27:35+02:00" "2015-09-16T10:27:35+02:00"
}, },
... ...
} }
o "seq" is a list whose key is "name", annotation "last-modified" is o "seq" is a list whose key is "name"; annotation "last-modified" is
added only to the first entry: added only to the first entry:
"seq": [ "seq": [
{ {
"@": { "@": {
"example-last-modified:last-modified": "example-last-modified:last-modified":
"2015-09-16T10:27:35+02:00" "2015-09-16T10:27:35+02:00"
}, },
"name": "one", "name": "one",
... ...
}, },
{ {
"name": "two", "name": "two",
... ...
} }
] ]
5.2.3. Adding Annotations to Anyxml and Leaf Instances 5.2.3. Adding Annotations to anyxml and leaf Instances
For an anyxml or leaf instance, the metadata object is added as a For an anyxml or leaf instance, the metadata object is added as a
sibling name/value pair whose name is the symbol "@" concatenated sibling name/value pair whose name is the symbol "@" concatenated
with the name of the leaf or anyxml member that is being annotated. with the name of the leaf or anyxml member that is being annotated.
The namespace part (module name) is included if and only if it is in The namespace part (module name) is included if and only if it is in
the name of the annotated member. the name of the annotated member.
Examples: Examples:
o "flag" is a leaf node of the "boolean" type defined in module o "flag" is a leaf node of the "boolean" type defined in module
"foo", and we assume the namespace name has to be expressed in its "foo", and we assume that the namespace name has to be expressed
JSON encoding: in its JSON encoding:
"foo:flag": true, "foo:flag": true,
"@foo:flag": { "@foo:flag": {
"example-last-modified:last-modified": "example-last-modified:last-modified":
"2015-09-16T10:27:35+02:00" "2015-09-16T10:27:35+02:00"
} }
o "stuff" is an anyxml node: o "stuff" is an anyxml node:
"stuff": [1, null, "three"], "stuff": [1, null, "three"],
"@stuff": { "@stuff": {
"example-last-modified:last-modified": "example-last-modified:last-modified":
"2015-09-16T10:27:35+02:00" "2015-09-16T10:27:35+02:00"
} }
5.2.4. Adding Annotations to Leaf-list Entries 5.2.4. Adding Annotations to leaf-list Entries
For a leaf-list entry, which is represented as a JSON array with For a leaf-list entry, which is represented as a JSON array with
values of a primitive type, annotations may be assigned to one or 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- more entries by adding a name/array pair as a sibling of the
list entry, where the name is symbol "@" concatenated with the name leaf-list entry, where the name is the symbol "@" concatenated with
of the leaf-list that is being annotated, and the value is a JSON the name of the leaf-list that is being annotated, and the value is a
array whose i-th element is the metadata object with annotations JSON array whose i-th element is the metadata object with annotations
assigned to the i-th entry of the leaf-list entry, or null if the assigned to the i-th entry of the leaf-list entry, or null if the
i-th entry has no annotations. i-th entry has no annotations.
Trailing null values in that array, i.e., those following the last Trailing null values in that array, i.e., those following the last
non-null metadata object, MAY be omitted. non-null metadata object, MAY be omitted.
For example, in the following leaf-list instance with four entries, For example, in the following leaf-list instance with four entries,
the "last-modified" annotation is added to the second and third entry the "last-modified" annotation is added to the second and third
in the following way: entries in the following way:
"bibliomod:folio": [6, 3, 7, 8], "bibliomod:folio": [6, 3, 7, 8],
"@bibliomod:folio": [ "@bibliomod:folio": [
null, null,
{ "example-last-modified:last-modified": { "example-last-modified:last-modified":
"2015-06-18T17:01:14+02:00" "2015-06-18T17:01:14+02:00"
}, },
{ "example-last-modified:last-modified": { "example-last-modified:last-modified":
"2015-09-16T10:27:35+02:00" "2015-09-16T10:27:35+02:00"
} }
skipping to change at page 13, line 15 skipping to change at page 14, line 15
6. Representing Annotations in DSDL Schemas 6. Representing Annotations in DSDL Schemas
[RFC6110] defines the standard mapping of YANG data models to [RFC6110] defines the standard mapping of YANG data models to
Document Schema Definition Languages (DSDL) [ISO.19757-1]. This Document Schema Definition Languages (DSDL) [ISO.19757-1]. This
section specifies the mapping for the extension statement section specifies the mapping for the extension statement
"md:annotation" (Section 7), which enables validation of XML instance "md:annotation" (Section 7), which enables validation of XML instance
documents containing metadata annotations. documents containing metadata annotations.
The first step of the DSDL mapping procedure, i.e., the The first step of the DSDL mapping procedure, i.e., the
transformation of the YANG data model to the hybrid schema (see transformation of the YANG data model to the hybrid schema (see
sec. 6 in [RFC6110]), is modified as follows: Section 6 in [RFC6110]), is modified as follows:
1. If the data model contains at least one "md:annotation" 1. If the data model contains at least one "md:annotation"
statement, then a RELAX NG named pattern definition MUST be added statement, then a RELAX NG [ISO.19757-2] named pattern definition
as a child of the root <rng:grammar> element in the hybrid MUST be added as a child of the root <rng:grammar> element in the
schema. It is RECOMMENDED to use the name "__yang_metadata__" hybrid schema. It is RECOMMENDED to use the name
for this named pattern. "__yang_metadata__" for this named pattern.
2. A reference to the named pattern described in item 1 MUST be 2. A reference to the named pattern described in item 1 MUST be
included as a child of every <rng:element> pattern that included as a child of every <rng:element> pattern that
corresponds to an anydata, container, leaf, leaf-list or list corresponds to an anydata, container, leaf, leaf-list, or list
data node. data node.
3. Every metadata annotation definition in the form 3. Every metadata annotation definition in the form
md:annotation ARGUMENT { md:annotation ARGUMENT {
... ...
} }
is mapped to the following RELAX NG pattern: is mapped to the following RELAX NG [ISO.19757-2] pattern:
<rng:optional> <rng:optional>
<rng:attribute name="PREFIX:ARGUMENT"> <rng:attribute name="PREFIX:ARGUMENT">
... ...
</rng:attribute> </rng:attribute>
</rng:optional> </rng:optional>
where PREFIX is the prefix bound to the namespace URI of the YANG where PREFIX is the prefix bound to the namespace URI of the YANG
module that contains the "md:annotation" statement. The above module that contains the "md:annotation" statement. The above
pattern SHALL be inserted as a child of the named pattern pattern SHALL be inserted as a child of the named pattern
described in item 1. described in item 1.
4. Substatements of "md:annotation" SHALL be mapped to children of 4. Substatements of "md:annotation" SHALL be mapped to children of
the "rng:attribute" pattern exactly as described in sec. 10 of the "rng:attribute" pattern exactly as described in Section 10 of
[RFC6110]. [RFC6110].
For example, the named pattern (item 1), when constructed only for For example, the named pattern (item 1), when constructed only for
the "last-modified" annotation, will have the following definition: the "last-modified" annotation, will have the following definition:
<rng:define name="__yang_metadata__"> <rng:define name="__yang_metadata__">
<rng:optional> <rng:optional>
<rng:attribute name="elm:last-modified"> <rng:attribute name="elm:last-modified">
<rng:ref name="ietf-yang-types__date-and-time"/> <rng:ref name="ietf-yang-types__date-and-time"/>
</rng:attribute> </rng:attribute>
</rng:optional> </rng:optional>
</rng:define> </rng:define>
Every "rng:element" pattern that corresponds to an anydata, Every "rng:element" pattern that corresponds to an anydata,
container, leaf, list or leaf-list data node will then contain a container, leaf, list, or leaf-list data node will then contain a
reference to the above named pattern, for example reference to the above named pattern; for example:
<rng:element name="foo:bar"> <rng:element name="foo:bar">
<rng:ref name="__yang_metadata__"/> <rng:ref name="__yang_metadata__"/>
... ...
</rng:element> </rng:element>
Note that it is not necessary to use such a reference for Note that it is not necessary to use such a reference for
"rng:element" patterns corresponding to anyxml data nodes because "rng:element" patterns corresponding to anyxml data nodes because
they already permit any XML attributes to be attached to their they already permit any XML attributes to be attached to their
instances. instances.
The second step of the DSDL mapping procedure, i.e., the The second step of the DSDL mapping procedure, i.e., the
transformation of the hybrid schema to RELAX NG, Schematron and DSRL transformation of the hybrid schema to RELAX NG [ISO.19757-2],
schemas, is unaffected by the inclusion of "md:annotation". Schematron [ISO.19757-3], and Document Semantics Renaming Language
(DSRL) [ISO.19757-8] schemas, is unaffected by the inclusion of
"md:annotation".
7. Metadata YANG Module 7. Metadata YANG Module
RFC Editor: In this section, replace all occurrences of 'XXXX' with <CODE BEGINS> file "ietf-yang-metadata@2016-08-05.yang"
the actual RFC number and all occurrences of the revision date below
with the date of RFC publication (and remove this note).
RFC Editor: Also please replace all occurrences of 'RFC 6020bis' with
the actual RFC number that will be assigned to
[I-D.ietf-netmod-rfc6020bis].
<CODE BEGINS> file "ietf-yang-metadata@2016-03-21.yang"
module ietf-yang-metadata { module ietf-yang-metadata {
namespace "urn:ietf:params:xml:ns:yang:ietf-yang-metadata"; namespace "urn:ietf:params:xml:ns:yang:ietf-yang-metadata";
prefix "md"; prefix "md";
organization organization
"IETF NETMOD (NETCONF Data Modeling Language) Working Group"; "IETF NETMOD (NETCONF Data Modeling Language) Working Group";
contact contact
"WG Web: <http://tools.ietf.org/wg/netmod/> "WG Web: <https://datatracker.ietf.org/wg/netmod/>
WG List: <mailto:netmod@ietf.org> WG List: <mailto:netmod@ietf.org>
WG Chair: Lou Berger WG Chair: Lou Berger
<mailto:lberger@labn.net> <mailto:lberger@labn.net>
WG Chair: Juergen Schoenwaelder
<mailto:j.schoenwaelder@jacobs-university.de>
WG Chair: Kent Watsen WG Chair: Kent Watsen
<mailto:kwatsen@juniper.net> <mailto:kwatsen@juniper.net>
Editor: Ladislav Lhotka Editor: Ladislav Lhotka
<mailto:lhotka@nic.cz>"; <mailto:lhotka@nic.cz>";
description description
"This YANG module defines an extension statement that allows for "This YANG module defines an 'extension' statement that allows
defining metadata annotations. for defining metadata annotations.
Copyright (c) 2016 IETF Trust and the persons identified as Copyright (c) 2016 IETF Trust and the persons identified as
authors of the code. All rights reserved. authors of the code. All rights reserved.
Redistribution and use in source and binary forms, with or Redistribution and use in source and binary forms, with or
without modification, is permitted pursuant to, and subject to without modification, is permitted pursuant to, and subject to
the license terms contained in, the Simplified BSD License set the license terms contained in, the Simplified BSD License set
forth in Section 4.c of the IETF Trust's Legal Provisions forth in Section 4.c of the IETF Trust's Legal Provisions
Relating to IETF Documents Relating to IETF Documents
(http://trustee.ietf.org/license-info). (http://trustee.ietf.org/license-info).
This version of this YANG module is part of RFC XXXX This version of this YANG module is part of RFC 7952
(http://tools.ietf.org/html/rfcXXXX); see the RFC itself for (http://www.rfc-editor.org/info/rfc7952); see the RFC itself
full legal notices."; for full legal notices.";
revision 2016-03-21 { revision 2016-08-05 {
description description
"Initial revision."; "Initial revision.";
reference reference
"RFC XXXX: Defining and Using Metadata with YANG"; "RFC 7952: Defining and Using Metadata with YANG";
} }
extension annotation { extension annotation {
argument name; argument name;
description description
"This extension allows for defining metadata annotations in "This extension allows for defining metadata annotations in
YANG modules. The 'md:annotation' statement can appear only at YANG modules. The 'md:annotation' statement can appear only
the top level of a YANG module or submodule, i.e. it becomes a at the top level of a YANG module or submodule, i.e., it
new alternative in the ABNF production rule for 'body-stmts' becomes a new alternative in the ABNF production rule for
(sec. 14 in RFC 6020bis). 'body-stmts' (Section 14 in RFC 7950).
The argument of the 'md:annotation' statement defines the name The argument of the 'md:annotation' statement defines the name
of the annotation. Syntactically it is a YANG identifier as of the annotation. Syntactically, it is a YANG identifier as
defined in RFC 6020bis, sec. 6.2. defined in Section 6.2 of RFC 7950.
An annotation defined with this extension statement inherits An annotation defined with this 'extension' statement inherits
the namespace and other context from the YANG module in which the namespace and other context from the YANG module in which
it is defined. it is defined.
Data type of the annotation value is specified in the same way The data type of the annotation value is specified in the same
as for a leaf data node using the 'type' statement. way as for a leaf data node using the 'type' statement.
Semantics of the annotation and other documentation can be The semantics of the annotation and other documentation can be
specified using the following standard YANG substatements (all specified using the following standard YANG substatements (all
are optional): 'description', 'if-feature', 'reference', are optional): 'description', 'if-feature', 'reference',
'status', and 'units'. 'status', and 'units'.
A server announces support for a particular annotation by A server announces support for a particular annotation by
including the module in which the annotation is defined among including the module in which the annotation is defined among
the advertised YANG modules (e.g., in NETCONF hello message or the advertised YANG modules, e.g., in a NETCONF <hello>
yang-library). The annotation then can be attached to any message or in the YANG library (RFC 7950). The annotation can
instance of data node defined in any YANG module that is then be attached to any instance of a data node defined in any
advertised by the server. YANG module that is advertised by the server.
XML and JSON encoding of annotations is defined in XML encoding and JSON encoding of annotations are defined in
RFC XXXX."; RFC 7952.";
} }
} }
<CODE ENDS> <CODE ENDS>
8. IANA Considerations 8. IANA Considerations
RFC Editor: In this section, replace all occurrences of 'XXXX' with This document registers a URI in the "IETF XML Registry" [RFC3688].
the actual RFC number and all occurrences of the revision date below
with the date of RFC publication (and remove this note).
This document registers a URI in the "IETF XML registry" [RFC3688].
Following the format in RFC 3688, the following registration has been Following the format in RFC 3688, the following registration has been
made. made.
--------------------------------------------------------------------- ---------------------------------------------------------------------
URI: urn:ietf:params:xml:ns:yang:ietf-yang-metadata URI: urn:ietf:params:xml:ns:yang:ietf-yang-metadata
Registrant Contact: The NETMOD WG of the IETF. Registrant Contact: The NETMOD WG of the IETF.
XML: N/A, the requested URI is an XML namespace. XML: N/A, the requested URI is an XML namespace.
--------------------------------------------------------------------- ---------------------------------------------------------------------
skipping to change at page 17, line 4 skipping to change at page 18, line 18
Following the format in RFC 3688, the following registration has been Following the format in RFC 3688, the following registration has been
made. made.
--------------------------------------------------------------------- ---------------------------------------------------------------------
URI: urn:ietf:params:xml:ns:yang:ietf-yang-metadata URI: urn:ietf:params:xml:ns:yang:ietf-yang-metadata
Registrant Contact: The NETMOD WG of the IETF. Registrant Contact: The NETMOD WG of the IETF.
XML: N/A, the requested URI is an XML namespace. XML: N/A, the requested URI is an XML namespace.
--------------------------------------------------------------------- ---------------------------------------------------------------------
This document registers a YANG module in the "YANG Module Names" This document registers a YANG module in the "YANG Module Names"
registry [RFC6020]. registry [RFC6020].
--------------------------------------------------------------------- ---------------------------------------------------------------------
name: ietf-yang-metadata Name: ietf-yang-metadata
namespace: urn:ietf:params:xml:ns:yang:ietf-yang-metadata Namespace: urn:ietf:params:xml:ns:yang:ietf-yang-metadata
prefix: md Prefix: md
reference: RFC XXXX Reference: RFC 7952
--------------------------------------------------------------------- ---------------------------------------------------------------------
9. Security Considerations 9. Security Considerations
This document introduces a mechanism for defining metadata This document introduces a mechanism for defining metadata
annotations in YANG modules and attaching them to instances of YANG annotations in YANG modules and attaching them to instances of YANG
data nodes. By itself, this mechanism represents no security threat. data nodes. By itself, this mechanism represents no security threat.
Security implications of a particular annotation defined using this Security implications of a particular annotation defined using this
mechanism MUST be duly considered and documented in the the mechanism MUST be duly considered and documented in the annotation's
annotation's definition. definition.
An annotation SHOULD be subject to the same or stricter access An annotation SHOULD be subject to the same or stricter access
control rules as the data node instance to which the annotation is control rules as the data node instance to which the annotation is
attached. It is RECOMMENDED that security-sensitive or privacy- attached. It is RECOMMENDED that security-sensitive or privacy-
sensitive data be modeled as regular YANG data nodes rather than sensitive data be modeled as regular YANG data nodes rather than
annotations. annotations.
10. Acknowledgments 10. References
The author wishes to thank Andy Bierman, Martin Bjorklund, Benoit
Claise, Juergen Schoenwaelder, and Kent Watsen for their helpful
comments and suggestions.
11. References
11.1. Normative References
[I-D.ietf-netmod-rfc6020bis]
Bjorklund, M., "The YANG 1.1 Data Modeling Language",
draft-ietf-netmod-rfc6020bis-11 (work in progress),
February 2016.
[I-D.ietf-netmod-yang-json] 10.1. Normative References
Lhotka, L., "JSON Encoding of Data Modeled with YANG",
draft-ietf-netmod-yang-json-09 (work in progress), March
2016.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>. <http://www.rfc-editor.org/info/rfc2119>.
[RFC3688] Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688, [RFC3688] Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,
DOI 10.17487/RFC3688, January 2004, DOI 10.17487/RFC3688, January 2004,
<http://www.rfc-editor.org/info/rfc3688>. <http://www.rfc-editor.org/info/rfc3688>.
skipping to change at page 18, line 33 skipping to change at page 19, line 37
[RFC6110] Lhotka, L., Ed., "Mapping YANG to Document Schema [RFC6110] Lhotka, L., Ed., "Mapping YANG to Document Schema
Definition Languages and Validating NETCONF Content", Definition Languages and Validating NETCONF Content",
RFC 6110, DOI 10.17487/RFC6110, February 2011, RFC 6110, DOI 10.17487/RFC6110, February 2011,
<http://www.rfc-editor.org/info/rfc6110>. <http://www.rfc-editor.org/info/rfc6110>.
[RFC7159] Bray, T., Ed., "The JavaScript Object Notation (JSON) Data [RFC7159] Bray, T., Ed., "The JavaScript Object Notation (JSON) Data
Interchange Format", RFC 7159, DOI 10.17487/RFC7159, March Interchange Format", RFC 7159, DOI 10.17487/RFC7159, March
2014, <http://www.rfc-editor.org/info/rfc7159>. 2014, <http://www.rfc-editor.org/info/rfc7159>.
[W3C.REC-xml-infoset-20040204] [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>.
[RFC7951] Lhotka, L., "JSON Encoding of Data Modeled with YANG",
RFC 7951, DOI 10.17487/RFC7951, August 2016,
<http://www.rfc-editor.org/info/rfc7951>.
[XML-INFOSET]
Cowan, J. and R. Tobin, "XML Information Set (Second Cowan, J. and R. Tobin, "XML Information Set (Second
Edition)", World Wide Web Consortium Recommendation REC- Edition)", World Wide Web Consortium Recommendation
xml-infoset-20040204, February 2004, REC-xml-infoset-20040204, February 2004,
<http://www.w3.org/TR/2004/REC-xml-infoset-20040204>. <http://www.w3.org/TR/2004/REC-xml-infoset-20040204>.
[W3C.REC-xml-names11-20060816] [XML-NAMES]
Bray, T., Hollander, D., Layman, A., and R. Tobin, Bray, T., Hollander, D., Layman, A., Tobin, R., and H.
"Namespaces in XML 1.1 (Second Edition)", World Wide Web Thompson, "Namespaces in XML 1.0 (Third Edition)", World
Consortium Recommendation REC-xml-names11-20060816, August Wide Web Consortium Recommendation REC-xml-names-20091208,
2006, December 2009,
<http://www.w3.org/TR/2006/REC-xml-names11-20060816>. <http://www.w3.org/TR/2009/REC-xml-names-20091208>.
11.2. Informative References
[I-D.ietf-netconf-restconf] 10.2. Informative References
Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF
Protocol", draft-ietf-netconf-restconf-10 (work in
progress), March 2016.
[ISO.19757-1] [ISO.19757-1]
International Organization for Standardization, "Document International Organization for Standardization,
Schema Definition Languages (DSDL) - Part 1: Overview", "Information Technology - Document Schema Definition
ISO/IEC 19757-1, November 2004. Languages (DSDL) - Part 1: Overview", ISO/IEC 19757-1,
September 2008.
[RFC6241] Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed.,
and A. Bierman, Ed., "Network Configuration Protocol
(NETCONF)", RFC 6241, DOI 10.17487/RFC6241, June 2011,
<http://www.rfc-editor.org/info/rfc6241>.
Appendix A. Change Log
RFC Editor: Remove this section upon publication as an RFC.
A.1. Changes Between Revisions -06 and -07
o Added sentence in Sec. 9 (Stephen Farrell's suggestion).
A.2. Changes Between Revisions -05 and -06
o Added explanation of why a YANG extension is used rather than a
built-in statement.
A.3. Changes Between Revisions -04 and -05
o Clarification regarding the type of an annotation.
A.4. Changes Between Revisions -03 and -04
o Added explanation of what "top level of a module" means.
A.5. Changes Between Revisions -02 and -03
o Section 4 was considerably simplified, also because member names
starting with "@" are now permitted by
[I-D.ietf-netmod-yang-json].
A.6. Changes Between Revisions -01 and -02
o The "type" statement became mandatory.
o Terminology section was extended.
o The annotation "inactive" defined in the example module was
replaced with "last-modified" that is supposedly less
controversial.
o Introduction now states limitation due to XML attribute
properties.
o A recommendation was added to define annotations in a module by
themselves.
o Section "Using Annotations" was added.
o An example for "anyxml" was added.
o RFC 6241 was moved to informative references.
A.7. Changes Between Revisions -00 and -01
o Define JSON encoding for annotations attached to 'anydata' nodes.
A.8. Changes Between draft-lhotka-netmod-yang-metadata-01 and draft- [ISO.19757-2]
ietf-netmod-yang-metadata-00 International Organization for Standardization,
"Information technology -- Document Schema Definition
Language (DSDL) -- Part 2: Regular-grammar-based
validation -- RELAX NG", ISO/IEC 19757-2:2008, December
2008.
o References to RFC 6020 were changed to the 6020bis I-D. [ISO.19757-3]
International Organization for Standardization,
"Information technology -- Document Schema Definition
Languages (DSDL) -- Part 3: Rule-based validation --
Schematron", ISO/IEC 19757-3:2016, January 2016.
o Text about RFC 2119 key words was added to "ietf-yang-metadata" [ISO.19757-8]
module description. International Organization for Standardization,
"Information Technology - Document Schema Definition
Languages (DSDL) - Part 8: Document Semantics Renaming
Language - DSRL", ISO/IEC 19757-8:2008(E), December 2008.
A.9. Changes Between draft-lhotka-netmod-yang-metadata-00 and -01 [RESTCONF] Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF
Protocol", Work in Progress,
draft-ietf-netconf-restconf-16, August 2016.
o Encoding of annotations for anyxml nodes was changed to be the [RFC6241] Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed.,
same as for leafs. This was necessary because anyxml value now and A. Bierman, Ed., "Network Configuration Protocol
needn't be an object. (NETCONF)", RFC 6241, DOI 10.17487/RFC6241, June 2011,
<http://www.rfc-editor.org/info/rfc6241>.
o It is stated that "md:annotation" statement defines only the Acknowledgements
syntax of an annotation.
o Allowed "if-feature" as a substatement of "md:annotation". The author wishes to thank Andy Bierman, Martin Bjorklund, Benoit
Claise, Juergen Schoenwaelder, and Kent Watsen for their helpful
comments and suggestions.
Author's Address Author's Address
Ladislav Lhotka Ladislav Lhotka
CZ.NIC CZ.NIC
Email: lhotka@nic.cz Email: lhotka@nic.cz
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