draft-ietf-netmod-yang-json-04.txt   draft-ietf-netmod-yang-json-05.txt 
NETMOD Working Group L. Lhotka NETMOD Working Group L. Lhotka
Internet-Draft CZ.NIC Internet-Draft CZ.NIC
Intended status: Standards Track June 12, 2015 Intended status: Standards Track September 10, 2015
Expires: December 14, 2015 Expires: March 13, 2016
JSON Encoding of Data Modeled with YANG JSON Encoding of Data Modeled with YANG
draft-ietf-netmod-yang-json-04 draft-ietf-netmod-yang-json-05
Abstract Abstract
This document defines encoding rules for representing configuration, This document defines encoding rules for representing configuration,
state data, RPC input and output parameters, and notifications state data, RPC operation or action input and output parameters, and
defined using YANG as JavaScript Object Notation (JSON) text. notifications defined using YANG as JavaScript Object Notation (JSON)
text.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/. Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on December 14, 2015. This Internet-Draft will expire on March 13, 2016.
Copyright Notice Copyright Notice
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology and Notation . . . . . . . . . . . . . . . . . . 3 2. Terminology and Notation . . . . . . . . . . . . . . . . . . 3
3. Validation of JSON-encoded 3. Properties of the JSON Encoding . . . . . . . . . . . . . . . 4
Instance Data . . . . . . . . . . . . . . . . . . . . . . . . 4
4. Names and Namespaces . . . . . . . . . . . . . . . . . . . . 4 4. Names and Namespaces . . . . . . . . . . . . . . . . . . . . 4
5. Encoding of YANG Data Node Instances . . . . . . . . . . . . 6 5. Encoding of YANG Data Node Instances . . . . . . . . . . . . 6
5.1. The "leaf" Data Node . . . . . . . . . . . . . . . . . . 7 5.1. The "leaf" Data Node . . . . . . . . . . . . . . . . . . 7
5.2. The "container" Data Node . . . . . . . . . . . . . . . . 7 5.2. The "container" Data Node . . . . . . . . . . . . . . . . 7
5.3. The "leaf-list" Data Node . . . . . . . . . . . . . . . . 7 5.3. The "leaf-list" Data Node . . . . . . . . . . . . . . . . 7
5.4. The "list" Data Node . . . . . . . . . . . . . . . . . . 8 5.4. The "list" Data Node . . . . . . . . . . . . . . . . . . 8
5.5. The "anydata" Data Node . . . . . . . . . . . . . . . . . 9 5.5. The "anydata" Data Node . . . . . . . . . . . . . . . . . 9
5.6. The "anyxml" Data Node . . . . . . . . . . . . . . . . . 10 5.6. The "anyxml" Data Node . . . . . . . . . . . . . . . . . 10
6. The Mapping of YANG Data Types to JSON Values . . . . . . . . 10 6. Representing YANG Data Types in JSON Values . . . . . . . . . 10
6.1. Numeric Types . . . . . . . . . . . . . . . . . . . . . . 10 6.1. Numeric Types . . . . . . . . . . . . . . . . . . . . . . 10
6.2. The "string" Type . . . . . . . . . . . . . . . . . . . . 11 6.2. The "string" Type . . . . . . . . . . . . . . . . . . . . 11
6.3. The "boolean" Type . . . . . . . . . . . . . . . . . . . 11 6.3. The "boolean" Type . . . . . . . . . . . . . . . . . . . 11
6.4. The "enumeration" Type . . . . . . . . . . . . . . . . . 11 6.4. The "enumeration" Type . . . . . . . . . . . . . . . . . 11
6.5. The "bits" Type . . . . . . . . . . . . . . . . . . . . . 11 6.5. The "bits" Type . . . . . . . . . . . . . . . . . . . . . 11
6.6. The "binary" Type . . . . . . . . . . . . . . . . . . . . 11 6.6. The "binary" Type . . . . . . . . . . . . . . . . . . . . 11
6.7. The "leafref" Type . . . . . . . . . . . . . . . . . . . 11 6.7. The "leafref" Type . . . . . . . . . . . . . . . . . . . 12
6.8. The "identityref" Type . . . . . . . . . . . . . . . . . 11 6.8. The "identityref" Type . . . . . . . . . . . . . . . . . 12
6.9. The "empty" Type . . . . . . . . . . . . . . . . . . . . 12 6.9. The "empty" Type . . . . . . . . . . . . . . . . . . . . 12
6.10. The "union" Type . . . . . . . . . . . . . . . . . . . . 13 6.10. The "union" Type . . . . . . . . . . . . . . . . . . . . 13
6.11. The "instance-identifier" Type . . . . . . . . . . . . . 13 6.11. The "instance-identifier" Type . . . . . . . . . . . . . 14
7. I-JSON Compliance . . . . . . . . . . . . . . . . . . . . . . 14 7. I-JSON Compliance . . . . . . . . . . . . . . . . . . . . . . 14
8. Security Considerations . . . . . . . . . . . . . . . . . . . 15 8. Security Considerations . . . . . . . . . . . . . . . . . . . 15
9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 15 9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 15
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 15 10. References . . . . . . . . . . . . . . . . . . . . . . . . . 15
10.1. Normative References . . . . . . . . . . . . . . . . . . 15 10.1. Normative References . . . . . . . . . . . . . . . . . . 15
10.2. Informative References . . . . . . . . . . . . . . . . . 16 10.2. Informative References . . . . . . . . . . . . . . . . . 16
Appendix A. A Complete Example . . . . . . . . . . . . . . . . . 16 Appendix A. A Complete Example . . . . . . . . . . . . . . . . . 16
Appendix B. Change Log . . . . . . . . . . . . . . . . . . . . . 18 Appendix B. Change Log . . . . . . . . . . . . . . . . . . . . . 18
B.1. Changes Between Revisions -03 and -04 . . . . . . . . . . 18 B.1. Changes Between Revisions -04 and -05 . . . . . . . . . . 18
B.2. Changes Between Revisions -02 and -03 . . . . . . . . . . 19 B.2. Changes Between Revisions -03 and -04 . . . . . . . . . . 18
B.3. Changes Between Revisions -01 and -02 . . . . . . . . . . 19 B.3. Changes Between Revisions -02 and -03 . . . . . . . . . . 19
B.4. Changes Between Revisions -00 and -01 . . . . . . . . . . 19 B.4. Changes Between Revisions -01 and -02 . . . . . . . . . . 19
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 19 B.5. Changes Between Revisions -00 and -01 . . . . . . . . . . 19
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 20
1. Introduction 1. Introduction
The NETCONF protocol [RFC6241] uses XML [W3C.REC-xml-20081126] for The NETCONF protocol [RFC6241] uses XML [W3C.REC-xml-20081126] for
encoding data in its Content Layer. Other management protocols might encoding data in its Content Layer. Other management protocols might
want to use other encodings while still benefiting from using YANG want to use other encodings while still benefiting from using YANG
[I-D.ietf-netmod-rfc6020bis] as the data modeling language. [I-D.ietf-netmod-rfc6020bis] as the data modeling language.
For example, the RESTCONF protocol [I-D.ietf-netconf-restconf] For example, the RESTCONF protocol [I-D.ietf-netconf-restconf]
supports two encodings: XML (media type "application/yang.data+xml") supports two encodings: XML (media type "application/yang.data+xml")
and JSON (media type "application/yang.data+json). and JSON (media type "application/yang.data+json).
The specification of YANG 1.1 data modelling language The specification of YANG 1.1 data modelling language
[I-D.ietf-netmod-rfc6020bis] defines only XML encoding for data [I-D.ietf-netmod-rfc6020bis] defines only XML encoding for data
instances, i.e., contents of configuration datastores, state data, instances, i.e., contents of configuration datastores, state data,
RFC input and output parameters, and event notifications. The aim of RPC operation or action input and output parameters, and event
this document is to define rules for encoding the same data as notifications. The aim of this document is to define rules for
JavaScript Object Notation (JSON) text [RFC7159]. encoding the same data as JavaScript Object Notation (JSON)
text [RFC7159].
In order to achieve maximum interoperability while allowing
implementations to use a variety of available JSON parsers, the JSON
encoding rules follow, as much as possible, the constraints of the
I-JSON restricted profile [RFC7493]. Section 7 discusses I-JSON
conformance in more detail.
2. Terminology and Notation 2. Terminology and Notation
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].
The following terms are defined in [I-D.ietf-netmod-rfc6020bis]: The following terms are defined in [I-D.ietf-netmod-rfc6020bis]:
o action,
o anydata, o anydata,
o anyxml, o anyxml,
o augment, o augment,
o container, o container,
o data node, o data node,
o data tree,
o identity, o identity,
o instance identifier, o instance identifier,
o leaf, o leaf,
o leaf-list, o leaf-list,
o list, o list,
o module, o module,
o RPC operation,
o submodule. o submodule.
3. Validation of JSON-encoded Instance Data 3. Properties of the JSON Encoding
Instance data validation as defined in [I-D.ietf-netmod-rfc6020bis], This document defines JSON encoding for YANG data trees and their
sec. 8.3.3, is only applicable to XML-encoded data. For one, subtrees. It is always assumed that the top-level structure in JSON-
semantic constraints in "must" statements are expressed using encoded data is an object.
XPath 1.0 [W3C.REC-xpath-19991116], which can be properly interpreted
only in the XML context.
This document and the corresponding "XML Mapping Rules" sections from Instances of YANG data nodes (leafs, containers, leaf-lists, lists,
[I-D.ietf-netmod-rfc6020bis] also define an implicit schema-driven anydata and anyxml nodes) are encoded as members of a JSON object,
mapping of JSON-encoded instances to XML-encoded instances (and vice i.e., name/value pairs. Section 4 defines how the name part is
versa). This mapping is mostly straightforward. In cases where formed, and the following sections deal with the value part.
doubts could arise, this document gives explicit instructions for
mapping JSON-encoded instances to XML.
In order to validate a JSON instance document, it needs first to be Unlike XML element content, JSON values carry partial type
mapped, at least conceptually, to the corresponding XML instance information (number, string, boolean). The JSON encoding is defined
document. By definition, the JSON document is then valid if and only so that this information is never in conflict with the data type of
if the XML document is valid according to the rules stated in the corresponding YANG leaf or leaf-list.
[I-D.ietf-netmod-rfc6020bis].
With the exception of anyxml and schema-less anydata nodes, it is
possible to map a JSON-encoded data tree to XML encoding as defined
in [I-D.ietf-netmod-rfc6020bis], and vice versa. However, such
conversions require the YANG data model to be available.
In order to achieve maximum interoperability while allowing
implementations to use a variety of existing JSON parsers, the JSON
encoding rules follow, as much as possible, the constraints of the
I-JSON restricted profile [RFC7493]. Section 7 discusses I-JSON
conformance in more detail.
4. Names and Namespaces 4. Names and Namespaces
Instances of YANG data nodes (leafs, containers, leaf-lists, lists, An object member name MUST be in one of the following forms:
anydata and anyxml nodes) are always encoded as members of a JSON
object, i.e., as name/value pairs. This section defines how the name
part is formed, and the following sections deal with the value part.
Except in the cases specified below, the member name is identical to o simple - identical to the identifier of the corresponding YANG
the identifier of the corresponding YANG data node. Every such name data node;
belongs to a namespace which is associated with the YANG module where
the corresponding data node is defined. If the data node is defined
in a submodule, then the namespace is determined by the main module
to which the submodule belongs.
If the namespace of a member name has to be explicitly specified, the o namespace-qualified - the data node identifier is prefixed with
module name SHALL be used as a prefix to the member's local name. the name of the module in which the data node is defined, and
Both parts of the member name SHALL be separated with a colon separated by the colon character (":").
character (":"). Using ABNF [RFC5234], the namespace-qualified name
can be expressed as shown in Figure 1, where the production for
"identifier" is defined in sec. 13 of [I-D.ietf-netmod-rfc6020bis].
qualified-member-name = identifier ":" identifier The name of a module determines the namespace of all data node names
defined in that module. If a data node is defined in a submodule,
then the namespace-qualified member name uses the name of the main
module to which the submodule belongs.
Figure 1: ABNF production for a qualified member name. ABNF syntax [RFC5234] of a member name is shown in Figure 1, where
the production for "identifier" is defined in sec. 13 of
[I-D.ietf-netmod-rfc6020bis].
Names with namespace identifiers in the form shown in Figure 1 are member-name = [identifier ":"] identifier
used if and only if the parent data node belongs to a different
namespace, which also includes all top-level YANG data nodes that Figure 1: ABNF production for a JSON member name.
have no parent node.
A namespace-qualified member name MUST be used for all members of a
top-level JSON object, and then also whenever the namespaces of the
data node and its parent node are different. In all other cases, the
simple form of the member name MUST be used.
For example, consider the following YANG module: For example, consider the following YANG module:
module foomod { module foomod {
namespace "http://example.com/foomod"; namespace "http://example.com/foomod";
prefix "foo"; prefix "foo";
container top { container top {
skipping to change at page 5, line 31 skipping to change at page 5, line 38
If the data model consists only of this module, then the following is If the data model consists only of this module, then the following is
a valid JSON-encoded configuration: a valid JSON-encoded configuration:
{ {
"foomod:top": { "foomod:top": {
"foo": 54 "foo": 54
} }
} }
Note that the top-level container instance contains the namespace Note that the member of the top-level object uses the namespace-
identifier (module name) but the "foo" leaf doesn't because it is qualified name but the "foo" leaf doesn't because it is defined in
defined in the same module as its parent container. the same module as its parent container "top".
Now, assume the container "top" is augmented from another module, Now, assume the container "top" is augmented from another module,
"barmod": "barmod":
module barmod { module barmod {
namespace "http://example.com/barmod"; namespace "http://example.com/barmod";
prefix "bar"; prefix "bar";
skipping to change at page 6, line 33 skipping to change at page 6, line 33
look like this: look like this:
{ {
"foomod:top": { "foomod:top": {
"foo": 54, "foo": 54,
"barmod:bar": true "barmod:bar": true
} }
} }
The name of the "bar" leaf is prefixed with the namespace identifier The name of the "bar" leaf is prefixed with the namespace identifier
because its parent is defined in a different module, hence it belongs because its parent is defined in a different module.
to another namespace.
Explicit namespace identifiers are sometimes needed when encoding Explicit namespace identifiers are sometimes needed when encoding
values of the "identityref" and "instances-identifier" types. The values of the "identityref" and "instances-identifier" types. The
same form as shown in Figure 1 is then used as well. See Sections same form of namespace-qualified name as defined above is then used.
6.8 and 6.11 for details. See Sections 6.8 and 6.11 for details.
5. Encoding of YANG Data Node Instances 5. Encoding of YANG Data Node Instances
Every complete JSON instance document, such as a configuration Every data node instance is encoded as a name/value pair where the
datastore content, is an object. Its members are instances of all name is formed from the data node identifier using the rules of
top-level data nodes defined by the YANG data model. Section 4. The value depends on the category of the data node as
explained in the following subsections.
Character encoding MUST be UTF-8. Character encoding MUST be UTF-8.
Any data node instance is encoded as a name/value pair where the name
is formed from the data node identifier using the rules of Section 4.
The value depends on the category of the data node as explained in
the following subsections.
5.1. The "leaf" Data Node 5.1. The "leaf" Data Node
A leaf instance is encoded as a name/value pair where the value can A leaf instance is encoded as a name/value pair where the value can
be a string, number, literal "true" or "false", or the special array be a string, number, literal "true" or "false", or the special array
"[null]", depending on the type of the leaf (see Section 6 for the "[null]", depending on the type of the leaf (see Section 6 for the
type encoding rules). type encoding rules).
Example: For the leaf node definition Example: For the leaf node definition
leaf foo { leaf foo {
skipping to change at page 9, line 19 skipping to change at page 9, line 19
}, },
{ {
"baz": "zag", "baz": "zag",
"foo": 0 "foo": 0
} }
] ]
5.5. The "anydata" Data Node 5.5. The "anydata" Data Node
Anydata data node is a new feature in YANG 1.1. It serves as a Anydata data node is a new feature in YANG 1.1. It serves as a
container for data that appear as normal YANG-modeled data, except container for an unknown set of nodes that however appear as normal
their data model is not a priori known. YANG-modeled data. A data model for anydata content may or may not
exist at run time. In the latter case, no universal mapping between
JSON- and XML-encoded instances is available.
An anydata instance is thus encoded in the same way as a container, An anydata instance is encoded in the same way as a container, i.e.,
and its content is subject to the following rules: as a value/object pair. The requirement that anydata content can be
modeled by YANG implies the following rules for JSON text inside the
object:
o It is a valid I-JSON message [RFC7493]. o It is valid I-JSON [RFC7493].
o Any member name is either a YANG identifier as defined by the o All object member names satisfy the ABNF production in Figure 1.
"identifier" production in sec. 13 of
[I-D.ietf-netmod-rfc6020bis], or two such identifiers separated by
the colon character (":"). See also Section 4.
o Any JSON array contains either only unique scalar values (as a o Any JSON array contains either only unique scalar values (as a
leaf-list, see Section 5.3), or only objects (as a list, see leaf-list, see Section 5.3), or only objects (as a list, see
Section 5.4). Section 5.4).
o The "null" value is only allowed in the single-element array o The "null" value is only allowed in the single-element array
"[null]" corresponding to the encoding of the "empty" type, see "[null]" corresponding to the encoding of the "empty" type, see
Section 6.9. Section 6.9.
If a data model for anydata content is not available, it may be
impossible to map a JSON-encoded anydata instance to XML, and vice
versa. Note, however, that such a mapping is not needed for
validation purposes (Section 3) because anydata contents are
generally not subject to YANG-based validation (see sec. 7.10 in
[I-D.ietf-netmod-rfc6020bis]).
Example: for the anydata definition Example: for the anydata definition
anydata data; anydata data;
the following is a valid JSON-encoded instance: the following is a valid JSON-encoded instance:
"data": { "data": {
"ietf-notification:notification": { "ietf-notification:notification": {
"eventTime": "2014-07-29T13:43:01Z", "eventTime": "2014-07-29T13:43:01Z",
"example-event:event": { "example-event:event": {
skipping to change at page 10, line 25 skipping to change at page 10, line 25
} }
} }
5.6. The "anyxml" Data Node 5.6. The "anyxml" Data Node
An anyxml instance is encoded as a JSON name/value pair which MUST An anyxml instance is encoded as a JSON name/value pair which MUST
satisfy I-JSON constraints. Otherwise it is unrestricted, i.e., the satisfy I-JSON constraints. Otherwise it is unrestricted, i.e., the
value can be an object, array, number, string or one of the literals value can be an object, array, number, string or one of the literals
"true", "false" and "null". "true", "false" and "null".
As in the case of anydata (Section 5.5), there is no universal There is no universal procedure for mapping JSON-encoded anyxml
procedure for mapping JSON-encoded anyxml instances to XML, and vice instances to XML, and vice versa.
versa.
Example: For the anyxml definition Example: For the anyxml definition
anyxml bar; anyxml bar;
the following is a valid JSON-encoded instance: the following is a valid JSON-encoded instance:
"bar": [true, null, true] "bar": [true, null, true]
6. The Mapping of YANG Data Types to JSON Values 6. Representing YANG Data Types in JSON Values
The type of the JSON value in an instance of the leaf or leaf-list The type of the JSON value in an instance of the leaf or leaf-list
data node depends on the type of that data node as specified in the data node depends on the type of that data node as specified in the
following subsections. following subsections.
6.1. Numeric Types 6.1. Numeric Types
A value of the "int8", "int16", "int32", "uint8", "uint16" and A value of the types "int8", "int16", "int32", "uint8", "uint16" and
"uint32" is represented as a JSON number. "uint32" is represented as a JSON number.
A value of the "int64", "uint64" or "decimal64" type is encoded as a A value of the "int64", "uint64" or "decimal64" type is represented
JSON string whose contents is the lexical representation of that as a JSON string whose content is the lexical representation of the
numeric value as specified in sections 9.2.1 and 9.3.1 of corresponding YANG type as specified in sections 9.2.1 and 9.3.1 of
[I-D.ietf-netmod-rfc6020bis]. [I-D.ietf-netmod-rfc6020bis].
For example, if the type of the leaf "foo" in Section 5.1 was For example, if the type of the leaf "foo" in Section 5.1 was
"uint64" instead of "uint8", the instance would have to be encoded as "uint64" instead of "uint8", the instance would have to be encoded as
"foo": "123" "foo": "123"
The special handling of 64-bit numbers follows from I-JSON The special handling of 64-bit numbers follows from the I-JSON
recommendation to encode numbers exceeding the IEEE 754-2008 double recommendation to encode numbers exceeding the IEEE 754-2008 double
precision range as strings, see sec. 2.2 in [RFC7493]. precision range as strings, see sec. 2.2 in [RFC7493].
6.2. The "string" Type 6.2. The "string" Type
A "string" value encoded as a JSON string, subject to JSON string A "string" value represented as a JSON string, subject to JSON string
encoding rules. encoding rules.
6.3. The "boolean" Type 6.3. The "boolean" Type
A "boolean" value is mapped to the corresponding JSON literal name A "boolean" value is represented as the corresponding JSON literal
"true" or "false". name "true" or "false".
6.4. The "enumeration" Type 6.4. The "enumeration" Type
An "enumeration" value is mapped in the same way as a string except An "enumeration" value is represented as a JSON string - one of the
that the permitted values are defined by "enum" statements in YANG. names assigned by "enum" statements in YANG.
See sec. 9.6 in [I-D.ietf-netmod-rfc6020bis].
The representation is identical to the lexical representation of the
"enumeration" type in XML, see sec. 9.6 in
[I-D.ietf-netmod-rfc6020bis].
6.5. The "bits" Type 6.5. The "bits" Type
A "bits" value is mapped to a JSON string identical to the lexical A "bits" value is represented as a JSON string - a space-separated
representation of this value in XML, i.e., space-separated names sequence of names of bits that are set. The permitted bit names are
representing the individual bit values that are set. See sec. 9.7 in assigned by "bit" statements in YANG.
[I-D.ietf-netmod-rfc6020bis].
The representation is identical to the lexical representation of the
"bits" type, see sec. 9.7 in [I-D.ietf-netmod-rfc6020bis].
6.6. The "binary" Type 6.6. The "binary" Type
A "binary" value is mapped to a JSON string identical to the lexical A "binary" value is represented as a JSON string - base64-encoding of
representation of this value in XML, i.e., base64-encoded binary arbitrary binary data.
data. See sec. 9.8 in [I-D.ietf-netmod-rfc6020bis].
The representation is identical to the lexical representation of the
"binary" type in XML, see sec. 9.8 in [I-D.ietf-netmod-rfc6020bis].
6.7. The "leafref" Type 6.7. The "leafref" Type
A "leafref" value is mapped according to the same rules as the type A "leafref" value is represented using the same rules as the type of
of the leaf being referred to. the leaf to which the leafref value refers.
6.8. The "identityref" Type 6.8. The "identityref" Type
An "identityref" value is mapped to a string representing the name of An "identityref" value is represented as a string - the name of an
an identity. Its namespace MUST be expressed as shown in Figure 1 if identity. If the identity is defined in another module than the leaf
it is different from the namespace of the leaf node containing the node containing the identityref value, the namespace-qualified form
identityref value, and MAY be expressed otherwise. (Section 4) MUST be used. Otherwise, both the simple and namespace-
qualified forms are permitted.
For example, consider the following schematic module: For example, consider the following schematic module:
module exmod { module exmod {
... ...
import ietf-interfaces { import ietf-interfaces {
prefix if; prefix if;
} }
import iana-if-type { import iana-if-type {
prefix ianaift; prefix ianaift;
skipping to change at page 12, line 35 skipping to change at page 12, line 46
A valid instance of the "type" leaf is then encoded as follows: A valid instance of the "type" leaf is then encoded as follows:
"type": "iana-if-type:ethernetCsmacd" "type": "iana-if-type:ethernetCsmacd"
The namespace identifier "iana-if-type" must be present in this case The namespace identifier "iana-if-type" must be present in this case
because the "ethernetCsmacd" identity is not defined in the same because the "ethernetCsmacd" identity is not defined in the same
module as the "type" leaf. module as the "type" leaf.
6.9. The "empty" Type 6.9. The "empty" Type
An "empty" value is mapped to "[null]", i.e., an array with the An "empty" value is represented as "[null]", i.e., an array with the
"null" literal being its only element. For the purposes of this "null" literal being its only element. For the purposes of this
document, "[null]" is treated as an atomic scalar value. document, "[null]" is considered an atomic scalar value.
This encoding of the "empty" type was chosen instead of using simply This encoding of the "empty" type was chosen instead of using simply
"null" in order to facilitate the use of empty leafs in common "null" in order to facilitate the use of empty leafs in common
programming languages. When used in a boolean context, the "[null]" programming languages where the "null" value of a member is treated
value, unlike "null", evaluates to true. as if the member is not present.
Example: For the leaf definition Example: For the leaf definition
leaf foo { leaf foo {
type empty; type empty;
} }
a valid instance is a valid instance is
"foo": [null] "foo": [null]
6.10. The "union" Type 6.10. The "union" Type
A value of the "union" type is encoded as the value of any of the A value of the "union" type is encoded as the value of any of the
member types. member types.
Unlike XML, JSON conveys part of the type information already in the When validating a value of the "union" type, the type information
encoding. When validating a value of the "union" type, this conveyed by the JSON encoding MUST also be taken into account.
information MUST also be taken into account.
For example, consider the following YANG definition: For example, consider the following YANG definition:
leaf bar { leaf bar {
type union { type union {
type uint16; type uint16;
type string; type string;
} }
} }
In RESTCONF [I-D.ietf-netconf-restconf], it is fully acceptable to In RESTCONF [I-D.ietf-netconf-restconf], it is possible to set the
set the value of "bar" in the following way when using the value of "bar" in the following way when using the "application/
"application/yang.data+xml" media type: yang.data+xml" media type:
<bar>13.5</bar> <bar>13.5</bar>
because the value may be interpreted as a string, i.e., the second because the value may be interpreted as a string, i.e., the second
member type of the union. When using the "application/ member type of the union. When using the "application/
yang.data+json" media type, however, this is an error: yang.data+json" media type, however, this is an error:
"bar": 13.5 "bar": 13.5
In this case, the JSON encoding indicates the value is supposed to be In this case, the JSON encoding indicates the value is supposed to be
a number rather than a string. a number rather than a string.
6.11. The "instance-identifier" Type 6.11. The "instance-identifier" Type
An "instance-identifier" value is encoded as a string that is An "instance-identifier" value is encoded as a string that is
analogical to the lexical representation in XML encoding, see analogical to the lexical representation in XML encoding, see
sec. 9.13.3 in [I-D.ietf-netmod-rfc6020bis]. However, the encoding sec. 9.13.3 in [I-D.ietf-netmod-rfc6020bis]. However, the encoding
of namespaces in instance-identifier values follows the rules stated of namespaces in instance-identifier values follows the rules stated
in Section 4, namely: in Section 4, namely:
o The namespace identifier is the module name where each data node o The leftmost (top-level) data node name is always in the
is defined. namespace-qualified form.
o The encoding of a node name with an explicit namespace is as shown
in Figure 1.
o The leftmost (top-level) node name is always prefixed with the
namespace identifier.
o Any subsequent node name has the namespace identifier if and only o Any subsequent data node name is in the namespace-qualified form
if its parent node has a different namespace. This also holds for if the node is defined in another module than its parent node, and
node names appearing in predicates. the simple form is used otherwise. This rule also holds for node
names appearing in predicates.
For example, For example,
/ietf-interfaces:interfaces/interface[name='eth0']/ietf-ip:ipv4/ip /ietf-interfaces:interfaces/interface[name='eth0']/ietf-ip:ipv4/ip
is a valid instance-identifer value because the data nodes is a valid instance-identifer value because the data nodes
"interfaces", "interface" and "name" are defined in the module "ietf- "interfaces", "interface" and "name" are defined in the module "ietf-
interfaces", whereas "ipv4" and "ip" are defined in "ietf-ip". interfaces", whereas "ipv4" and "ip" are defined in "ietf-ip".
When translating an instance-identifier value from JSON to XML, the
namespace identifier (YANG module name) in each component of the
instance-identifier MUST be replaced by an XML namespace prefix that
is associated with the namespace URI reference of the module in the
scope of the element containing the instance-identifier value.
7. I-JSON Compliance 7. I-JSON Compliance
I-JSON [RFC7493] is a restricted profile of JSON that guarantees I-JSON [RFC7493] is a restricted profile of JSON that guarantees
maximum interoperability for protocols that use JSON in their maximum interoperability for protocols that use JSON in their
messages, no matter what JSON encoders/decoders are used in protocol messages, no matter what JSON encoders/decoders are used in protocol
implementations. The encoding defined in this document therefore implementations. The encoding defined in this document therefore
observes the I-JSON requirements and recommendations as closely as observes the I-JSON requirements and recommendations as closely as
possible. possible.
In particular, the following properties are guaranteed: In particular, the following properties are guaranteed:
o Character encoding is UTF-8. o Character encoding is UTF-8.
o Member names within the same JSON object are always unique. o Member names within the same JSON object are always unique.
o The order of JSON object members is never relied upon. o The order of JSON object members is never relied upon.
o Numbers of any type supported by YANG can be exchanged reliably. o Numbers of any type supported by YANG can be exchanged reliably.
See Section 6.1 for details. See Section 6.1 for details.
This document deviates from I-JSON only in the encoding of values The JSON encoding defined in this document deviates from I-JSON only
with the "binary" type. It uses the base64 encoding scheme in the representation of the "binary" type. In order to remain
compatible with XML encoding, the base64 encoding scheme is used
(Section 6.6), whereas I-JSON recommends base64url instead. (Section 6.6), whereas I-JSON recommends base64url instead.
Theoretically, values of the "binary" type might appear in URI
references, such as Request-URI in RESTCONF, although in practice the
cases where it is really needed should be extremely rare.
8. Security Considerations 8. Security Considerations
This document defines an alternative encoding for data modeled in the This document defines an alternative encoding for data modeled in the
YANG data modeling language. As such, it doesn't contribute any new YANG data modeling language. As such, it doesn't contribute any new
security issues beyond those discussed in sec. 16 of security issues beyond those discussed in sec. 16 of
[I-D.ietf-netmod-rfc6020bis]. [I-D.ietf-netmod-rfc6020bis].
JSON processing is rather different from XML, and JSON parsers may JSON processing is rather different from XML, and JSON parsers may
thus suffer from other types of vulnerabilities than their XML thus suffer from other types of vulnerabilities than their XML
skipping to change at page 15, line 32 skipping to change at page 15, line 32
Bogdanovic, Balazs Lengyel, Juergen Schoenwaelder and Phil Shafer for Bogdanovic, Balazs Lengyel, Juergen Schoenwaelder and Phil Shafer for
their helpful comments and suggestions. their helpful comments and suggestions.
10. References 10. References
10.1. Normative References 10.1. Normative References
[I-D.ietf-netmod-rfc6020bis] [I-D.ietf-netmod-rfc6020bis]
Bjorklund, M., "YANG - A Data Modeling Language for the Bjorklund, M., "YANG - A Data Modeling Language for the
Network Configuration Protocol (NETCONF)", draft-ietf- Network Configuration Protocol (NETCONF)", draft-ietf-
netmod-rfc6020bis-05 (work in progress), May 2015. netmod-rfc6020bis-06 (work in progress), July 2015.
[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, March 1997. Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/
RFC2119, March 1997,
[RFC5234] Crocker, D. and P. Overell, "Augmented BNF for Syntax <http://www.rfc-editor.org/info/rfc2119>.
Specifications: ABNF", STD 68, RFC 5234, January 2008.
[RFC6241] Enns, R., Bjorklund, M., Schoenwaelder, J., and A. [RFC5234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
Bierman, "Network Configuration Protocol (NETCONF)", RFC Specifications: ABNF", STD 68, RFC 5234, DOI 10.17487/
6241, June 2011. RFC5234, January 2008,
<http://www.rfc-editor.org/info/rfc5234>.
[RFC7159] Bray, T., "The JavaScript Object Notation (JSON) Data [RFC6241] Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed.,
Interchange Format", RFC 7159, March 2014. and A. Bierman, Ed., "Network Configuration Protocol
(NETCONF)", RFC 6241, DOI 10.17487/RFC6241, June 2011,
<http://www.rfc-editor.org/info/rfc6241>.
[RFC7493] Bray, T., "The I-JSON Message Format", RFC 7493, March [RFC7159] Bray, T., Ed., "The JavaScript Object Notation (JSON) Data
2015. Interchange Format", RFC 7159, DOI 10.17487/RFC7159, March
2014, <http://www.rfc-editor.org/info/rfc7159>.
[W3C.REC-xml-20081126] [RFC7493] Bray, T., Ed., "The I-JSON Message Format", RFC 7493, DOI
Bray, T., Paoli, J., Sperberg-McQueen, M., Maler, E., and 10.17487/RFC7493, March 2015,
F. Yergeau, "Extensible Markup Language (XML) 1.0 (Fifth <http://www.rfc-editor.org/info/rfc7493>.
Edition)", World Wide Web Consortium Recommendation REC-
xml-20081126, November 2008,
<http://www.w3.org/TR/2008/REC-xml-20081126>.
10.2. Informative References 10.2. Informative References
[I-D.ietf-netconf-restconf] [I-D.ietf-netconf-restconf]
Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF
Protocol", draft-ietf-netconf-restconf-05 (work in Protocol", draft-ietf-netconf-restconf-07 (work in
progress), June 2015. progress), July 2015.
[RFC7223] Bjorklund, M., "A YANG Data Model for Interface [RFC7223] Bjorklund, M., "A YANG Data Model for Interface
Management", RFC 7223, May 2014. Management", RFC 7223, DOI 10.17487/RFC7223, May 2014,
<http://www.rfc-editor.org/info/rfc7223>.
[W3C.REC-xpath-19991116] [W3C.REC-xml-20081126]
Clark, J. and S. DeRose, "XML Path Language (XPath) Bray, T., Paoli, J., Sperberg-McQueen, M., Maler, E., and
Version 1.0", World Wide Web Consortium Recommendation F. Yergeau, "Extensible Markup Language (XML) 1.0 (Fifth
REC-xpath-19991116, November 1999, Edition)", World Wide Web Consortium Recommendation REC-
<http://www.w3.org/TR/1999/REC-xpath-19991116>. xml-20081126, November 2008,
<http://www.w3.org/TR/2008/REC-xml-20081126>.
Appendix A. A Complete Example Appendix A. A Complete Example
The JSON document shown below represents the same data as the reply The JSON document shown below represents the same data as the reply
to the NETCONF <get> request appearing in Appendix D of [RFC7223]. to the NETCONF <get> request appearing in Appendix D of [RFC7223].
The data model is a combination of two YANG modules: "ietf- The data model is a combination of two YANG modules: "ietf-
interfaces" and "ex-vlan" (the latter is an example module from interfaces" and "ex-vlan" (the latter is an example module from
Appendix C of [RFC7223]). The "if-mib" feature defined in the "ietf- Appendix C of [RFC7223]). The "if-mib" feature defined in the "ietf-
interfaces" module is considered to be active. interfaces" module is considered to be active.
skipping to change at page 18, line 37 skipping to change at page 18, line 36
} }
} }
] ]
} }
} }
Appendix B. Change Log Appendix B. Change Log
RFC Editor: Remove this section upon publication as an RFC. RFC Editor: Remove this section upon publication as an RFC.
B.1. Changes Between Revisions -03 and -04 B.1. Changes Between Revisions -04 and -05
o Removed section "Validation of JSON-encoded Instance Data" and
other text about XML-JSON mapping.
o Added section "Properties of the JSON Encoding".
B.2. Changes Between Revisions -03 and -04
o I-D.ietf-netmod-rfc6020bis is used as a normative reference o I-D.ietf-netmod-rfc6020bis is used as a normative reference
instead of RFC 6020. instead of RFC 6020.
o Removed noncharacters as an I-JSON issue because it doesn't exist o Removed noncharacters as an I-JSON issue because it doesn't exist
in YANG 1.1. in YANG 1.1.
o Section about anydata encoding was added. o Section about anydata encoding was added.
o Require I-JSON for anyxml encoding. o Require I-JSON for anyxml encoding.
o Use ABNF for defining qualified name. o Use ABNF for defining qualified name.
B.2. Changes Between Revisions -02 and -03 B.3. Changes Between Revisions -02 and -03
o Namespace encoding is defined without using RFC 2119 keywords. o Namespace encoding is defined without using RFC 2119 keywords.
o Specification for anyxml nodes was extended and clarified. o Specification for anyxml nodes was extended and clarified.
o Text about ordering of list entries was corrected. o Text about ordering of list entries was corrected.
B.3. Changes Between Revisions -01 and -02 B.4. Changes Between Revisions -01 and -02
o Encoding of namespaces in instance-identifiers was changed. o Encoding of namespaces in instance-identifiers was changed.
o Text specifying the order of array elements in leaf-list and list o Text specifying the order of array elements in leaf-list and list
instances was added. instances was added.
B.4. Changes Between Revisions -00 and -01 B.5. Changes Between Revisions -00 and -01
o Metadata encoding was moved to a separate I-D, draft-lhotka- o Metadata encoding was moved to a separate I-D, draft-lhotka-
netmod-yang-metadata. netmod-yang-metadata.
o JSON encoding is now defined directly rather than via XML-JSON o JSON encoding is now defined directly rather than via XML-JSON
mapping. mapping.
o The rules for namespace encoding has changed. This affect both o The rules for namespace encoding has changed. This affect both
node instance names and instance-identifiers. node instance names and instance-identifiers.
 End of changes. 69 change blocks. 
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