Internet DRAFT - draft-wright-json-schema-hyperschema
draft-wright-json-schema-hyperschema
Internet Engineering Task Force A. Wright, Ed.
Internet-Draft
Intended status: Informational H. Andrews, Ed.
Expires: October 17, 2017 Cloudflare, Inc.
G. Luff
April 15, 2017
JSON Hyper-Schema: A Vocabulary for Hypermedia Annotation of JSON
draft-wright-json-schema-hyperschema-01
Abstract
JSON Schema is a JSON based format for defining the structure of JSON
data. This document specifies hyperlink- and hypermedia-related
keywords of JSON Schema for annotating JSON documents with hyperlinks
and instructions for processing and manipulating remote JSON
resources through hypermedia environments like HTTP.
Note to Readers
The issues list for this draft can be found at <https://github.com/
json-schema-org/json-schema-spec/issues>.
For additional information, see <http://json-schema.org/>.
To provide feedback, use this issue tracker, the communication
methods listed on the homepage, or email the document editors.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on October 17, 2017.
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Copyright Notice
Copyright (c) 2017 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
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to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Conventions and Terminology . . . . . . . . . . . . . . . . . 3
3. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 3
3.1. Interaction with validation . . . . . . . . . . . . . . . 5
4. Meta-schema . . . . . . . . . . . . . . . . . . . . . . . . . 5
5. Schema keywords . . . . . . . . . . . . . . . . . . . . . . . 5
5.1. base . . . . . . . . . . . . . . . . . . . . . . . . . . 5
5.2. links . . . . . . . . . . . . . . . . . . . . . . . . . . 6
5.3. media . . . . . . . . . . . . . . . . . . . . . . . . . . 7
5.3.1. Properties of "media" . . . . . . . . . . . . . . . . 7
5.3.2. Example . . . . . . . . . . . . . . . . . . . . . . . 8
5.4. readOnly . . . . . . . . . . . . . . . . . . . . . . . . 8
6. Link Description Object . . . . . . . . . . . . . . . . . . . 9
6.1. Links, operations, and data . . . . . . . . . . . . . . . 9
6.1.1. Resolving templated URIs . . . . . . . . . . . . . . 9
6.1.2. Manipulating the target resource representation . . . 10
6.1.3. Submitting data for processing . . . . . . . . . . . 10
6.2. href . . . . . . . . . . . . . . . . . . . . . . . . . . 10
6.2.1. URI Templating . . . . . . . . . . . . . . . . . . . 11
6.3. hrefSchema . . . . . . . . . . . . . . . . . . . . . . . 12
6.4. rel . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
6.4.1. Security Considerations for "self" links . . . . . . 16
6.5. title . . . . . . . . . . . . . . . . . . . . . . . . . . 17
6.6. targetSchema . . . . . . . . . . . . . . . . . . . . . . 17
6.6.1. "targetSchema" and HTTP . . . . . . . . . . . . . . . 17
6.6.2. Security Considerations for "targetSchema" . . . . . 17
6.7. mediaType . . . . . . . . . . . . . . . . . . . . . . . . 19
6.7.1. Security concerns for "mediaType" . . . . . . . . . . 20
6.8. submissionEncType . . . . . . . . . . . . . . . . . . . . 21
6.9. submissionSchema . . . . . . . . . . . . . . . . . . . . 22
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 23
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7.1. Normative References . . . . . . . . . . . . . . . . . . 23
7.2. Informative References . . . . . . . . . . . . . . . . . 23
Appendix A. Acknowledgments . . . . . . . . . . . . . . . . . . 25
Appendix B. Change Log . . . . . . . . . . . . . . . . . . . . . 25
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 26
1. Introduction
JSON Schema is a JSON based format for defining the structure of JSON
data. This document specifies hyperlink- and hypermedia-related
keywords of JSON Schema.
The term JSON Hyper-Schema is used to refer to a JSON Schema that
uses these keywords.
This specification will use the terminology defined by the JSON
Schema core specification [json-schema]. It is advised that readers
have a copy of this specification.
2. Conventions and Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119].
The terms "schema" and "instance" are to be interpreted as defined in
the JSON Schema core specification [json-schema].
3. Overview
This document describes how JSON Schema can be used to define
hyperlinks on instance data. It also defines how to provide
additional information required to interpret JSON data as rich
multimedia documents.
As with all JSON Schema keywords, all the keywords described in the
"Schema Keywords" section are optional. The minimal valid JSON
Hyper-schema is the blank object.
Here is an example JSON Schema defining hyperlinks, and providing a
multimedia interpretation for the "imgData" property:
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{
"title": "Written Article",
"type": "object",
"properties": {
"id": {
"title": "Article Identifier",
"type": "number",
"readOnly": true
},
"title": {
"title": "Article Title",
"type": "string"
},
"authorId": {
"type": "integer"
},
"imgData": {
"title": "Article Illustration (thumbnail)",
"type": "string",
"media": {
"binaryEncoding": "base64",
"type": "image/png"
}
}
},
"required" : ["id", "title", "authorId"],
"links": [
{
"rel": "self",
"href": "/article{?id}"
},
{
"rel": "author",
"href": "/user?id={authorId}"
}
]
}
This example schema defines the properties of the instance. For the
"imgData" property, it specifies that that it should be
base64-decoded and the resulting binary data treated as a PNG image.
It also defines link relations for the instance, with URIs
incorporating values from the instance. [[CREF1: "id" probably
should not normally be a required keyword, since new instances will
have an unknown "id" property until is it assigned by the server.
However, this property is used in a link, and without it, multiple
different instances would be given the same rel=self URI!]]
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An example of a JSON instance described by the above schema might be:
{
"id": 15,
"title": "Example data",
"authorId": 105,
"imgData": "iVBORw...kJggg=="
}
The base-64 data has been abbreviated for readability.
3.1. Interaction with validation
Hyper-schemas MUST NOT be applied to an instance if the instance
fails to validate against the validation keywords within or
containing the hyper-schema. Hyper-schema keywords in branches of an
"anyOf" or "oneOf" that do not validate, or in a "dependencies"
subschema that is not relevant to the instance, MUST be ignored.
Hyper-schema keywords in a subschema contained within a "not", at any
depth, including any number of intervening additional "not"
subschemas, MUST be ignored.
If the subschema for a "contains" keyword contains hyper-schema
keywords they MUST be applied to all array elements that validate
against the schema. While finding a single validating element is
sufficient to determine the validation outcome, when hyper-schema
keywords are present, the subschema MUST be evaluated against all
array elements.
4. Meta-schema
The current URI for the JSON Schema Validation is <http://json-
schema.org/draft-06/hyper-schema#>.
5. Schema keywords
5.1. base
If present, this keyword is resolved against the current URI base
that the entire instance is found within, and sets the new URI base
for URI references within the instance. It is therefore the first
URI Reference resolved, regardless of which order it was found in.
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The URI is computed from the provided URI template using the same
process described for the "href" (Section 6.2) property of a Link
Description Object.
An example of a JSON schema using "base":
{
"base": "/object/{id}",
"links": [
{
"rel": "self",
"href": ""
},
{
"rel": "next",
"href": "{nextId}"
}
]
}
An example of a JSON instance using this schema to produce rel="self"
and rel="next" links:
{
"id": 41,
"nextId": 42
}
If the document URI is <http://example.com/?id=41>, then the new URI
base becomes <http://example.com/object/41>
Resolving the two Link Description Objects against this URI base
creates two links exactly equivalent to these absolute-form HTTP Link
headers:
o Link: <http://example.com/object/41>;rel=self
o Link: <http://example.com/object/42>;rel=next
5.2. links
The "links" property of schemas is used to associate Link Description
Objects with instances. The value of this property MUST be an array,
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and the items in the array must be Link Description Objects, as
defined below.
An example schema using the "links" keyword could be:
{
"title": "Schema defining links",
"links": [
{
"rel": "self",
"href": "{id}"
},
{
"rel": "parent",
"href": "{parent}"
}
]
}
5.3. media
The "media" property indicates that this instance contains non-JSON
data encoded in a JSON string. It describes the type of content and
how it is encoded.
The value of this property MUST be an object. The value of this
property SHOULD be ignored if the instance described is not a string.
5.3.1. Properties of "media"
The value of the "media" keyword MAY contain any of the following
properties:
5.3.1.1. binaryEncoding
If the instance value is a string, this property defines that the
string SHOULD be interpreted as binary data and decoded using the
encoding named by this property. RFC 2045, Sec 6.1 [RFC2045] lists
the possible values for this property.
5.3.1.2. type
The value of this property must be a media type, as defined by RFC
2046 [RFC2046]. This property defines the media type of instances
which this schema defines.
If the "binaryEncoding" property is not set, but the instance value
is a string, then the value of this property SHOULD specify a text
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document type, and the character set SHOULD be the character set into
which the JSON string value was decoded (for which the default is
Unicode).
5.3.2. Example
Here is an example schema, illustrating the use of "media":
{
"type": "string",
"media": {
"binaryEncoding": "base64",
"type": "image/png"
}
}
Instances described by this schema should be strings, and their
values should be interpretable as base64-encoded PNG images.
Another example:
{
"type": "string",
"media": {
"type": "text/html"
}
}
Instances described by this schema should be strings containing HTML,
using whatever character set the JSON string was decoded into
(default is Unicode).
5.4. readOnly
If it has a value of boolean true, this keyword indicates that the
value of the instance is managed exclusively by the server or the
owning authority, and attempts by a user agent to modify the value of
this property are expected to be ignored or rejected by a server.
For example, this property would be used to mark a server-generated
serial number as read-only.
The value of this keyword MUST be a boolean. The default value is
false.
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6. Link Description Object
A Link Description Object (LDO) is used to describe a single link
relation from the instance to another resource. A Link Description
Object must be an object.
The link description format can be used without JSON Schema, and use
of this format can be declared by referencing the normative link
description schema as the schema for the data structure that uses the
links. The URI of the normative link description schema is:
http://json-schema.org/draft-06/links (draft-06 version).
6.1. Links, operations, and data
[[CREF2: Note that while the current draft does not provide a way to
explicity indicate HTTP method support, some way of providing a non-
authoritative hint may be added in a future draft (see issue #73 in
the GitHub repository). ]]
There are several ways that a client can use data can with a link:
URI Template variables resolved from server-supplied instance data
URI Template variables resolved from user agent data
Replacing or modifying the target resource's representation
Submitting data for processing, where the data has no inherent
relation to the target resource's representation
The three ways to use client-supplied data are each addressed by a
separate schema keyword within the link description object. Link
operations ignore schemas that are not relevant to their semantics.
Link Description Objects do not directly indicate what operations,
such as HTTP methods, are supported by the target resource. Instead,
operations should be inferred primarily from link relation types
(Section 6.4) and URI schemes. Note, however, that a resource may
always decline an operation at runtime, for instance due to
application state that controls the operation's availability.
6.1.1. Resolving templated URIs
URI Template variables in "href" (Section 6.2) resolve from server-
supplied instance data by default. "hrefSchema" (Section 6.3) allows
a link to specify a schema for resolving template variables from
client-supplied data. Regular JSON Schema validation features can be
used to require resolution from user agent data, forbid it, or allow
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user agent data while falling back to server-supplied instance data
if no user agent data is provided.
The common pattern of resolving a templated path component with
server-supplied instance data while accepting user agent data to
build a query string can be implemented by setting the "hrefSchema"
subschemas for the path template variables to false, while giving the
query string template variables names that do not appear in the
instance. This ensures that the path variables can only be resolved
from the instance, and the query string variables can only be
resolved from user agent data. See the "hrefSchema" section for an
example of this approach.
6.1.2. Manipulating the target resource representation
In JSON Hyper-Schema, "targetSchema" (Section 6.6) supplies a non-
authoritative description of the target resource's representation. A
client can use "targetSchema" to structure input for replacing or
modifying the representation. Alternatively, if "targetSchema" is
absent or if the client prefers to only use authoritative
information, it can interact with the target resource to confirm or
discover its representation structure.
"targetSchema" is not intended to describe link operation responses,
except when the response semantics indicate that it is a
representation of the target resource. In all cases, the schema
indicated by the response itself is authoritative. See the
Section 6.6.1 for guidance specific to each HTTP method when using
"targetSchema" with HTTP URIs.
6.1.3. Submitting data for processing
The "submissionSchema" (Section 6.9) and "submissionEncType"
(Section 6.8) keywords describe the domain of the processing function
implemented by the target resource. Otherwise, as noted above, the
submission schema and encoding are ignored for operations to which
they are not relevant.
6.2. href
The value of the "href" link description property is a template used
to determine the target URI of the related resource. The value of
the instance property MUST be resolved as a URI-reference [RFC3986]
against the base URI of the instance.
This property is REQUIRED.
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6.2.1. URI Templating
[[CREF3: The pre-processing rules present in earlier drafts have been
removed due to their complexity and inability to address all
limitations with URI templating. This section is subject to
significant change in upcoming drafts to replace the old pre-
processing with a comprehensive solution. ]]
The value of "href" is to be used as a URI Template, as defined in
RFC 6570 [RFC6570]. However, some special considerations apply:
6.2.1.1. Values for substitution
The URI Template is filled out using data from some combination of an
external source and the instance. Where either instance data or user
agent data may be used, this section will refer simply to "data" or
to a "value". When the source is important, it is specified
explicitly. To allow the use of any object property (including the
empty string) or array index, the following rules are defined:
For a given variable name in the URI Template, the value to use is
determined as follows:
If the data is an array, and the variable name is a representation
of a non-negative integer, then the value at the corresponding
array index MUST be used (if it exists).
Otherwise, the variable name should be percent-decoded, and the
corresponding object property MUST be used (if it exists).
If "hrefSchema" (Section 6.3) is present and user agent data is
provided, the data MUST be a valid instance according to the value of
"hrefSchema". Template variables, after the process listed above,
MUST first be resolved from the user agent data instance. Any
variables left unresolved MUST be resolved from the resource instance
data.
6.2.1.1.1. Converting to strings
When any value referenced by the URI template is null, a boolean or a
number, then it should first be converted into a string as follows:
null values SHOULD be replaced by the text "null"
boolean values SHOULD be replaced by their lower-case equivalents:
"true" or "false"
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numbers SHOULD be replaced with their original JSON
representation.
In some software environments the original JSON representation of a
number will not be available (there is no way to tell the difference
between 1.0 and 1), so any reasonable representation should be used.
Schema and API authors should bear this in mind, and use other types
(such as string or boolean) if the exact representation is important.
6.2.1.2. Missing values
Sometimes, the appropriate values will not be available. For
example, the template might specify the use of object properties, but
no such data was provided (or "hrefSchema" is not present), and the
instance is an array or a string.
If any of the values required for the template are neither present in
the user agent data (if relevant) nor the JSON instance, then
substitute values MAY be provided from another source (such as
default values). Otherwise, the link definition SHOULD be considered
not to apply to the instance.
6.3. hrefSchema
The value of the "hrefSchema" link description property MUST be a
valid JSON Schema. This schema is used to validate user input or
other user agent data for filling out the URI Template in "href"
(Section 6.2), as described in that section.
Omitting "hrefSchema" or setting the entire schema to "false"
prevents any user agent data from being accepted.
Implementations MUST NOT attempt to validate values resolved from
resource instance data with "hrefSchema". This allows for different
validation rules for user agent data, such as supporting spelled-out
months for date-time input but using the standard date-time format
for storage.
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For example, this defines a schema for each of the query string
parameters in the URI template:
{
"href": "/foos{?condition,count,query}",
"hrefSchema": {
"properties": {
"condition": {
"type": "boolean",
"default": true
},
"count": {
"type": "integer",
"minimum": 0,
"default": 0
},
"query": {
"type": "string"
}
}
}
}
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In this example, the schema for "extra" is given as a reference to
keep the user agent data validation constraints identical to the
instance validation constraints for the corresponding property, while
"id" is given a false schema to prevent user agent data for that
variable.
{
"definitions": {
"extra": {
"type": "string",
"maxLength": 32
}
},
"type": "object",
"properties": {
"id": {
"type": "integer",
"minimum": 1,
"readOnly": true
},
"extra": {"$ref": "#/definitions/extra"}
},
"links": [{
"rel": "self",
"href": "/things/{id}{?extra}",
"hrefSchema": {
"properties": {
"id": false,
"extra": {"$ref": "#/definitions/extra"}
}
}
}]
}
[[CREF4: The above example simulates the behavior handled in earlier
drafts with a "method" of "get" by using the new "hrefSchema"
keyword. ]]
6.4. rel
The value of the "rel" property indicates the name of the relation to
the target resource. The value MUST be a registered link relation
from the IANA Link Relation Type Registry established in RFC 5988
[RFC5988], or a normalized URI following the URI production of RFC
3986 [RFC3986].
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The relation to the target is interpreted as from the instance that
the schema (or sub-schema) applies to, not any larger document that
the instance may have been found in.
Relationship definitions are not normally media type dependent, and
users are encouraged to utilize existing accepted relation
definitions.
For example, if a hyper-schema is defined:
{
"type": "array",
"items": {
"links": [{
"rel": "item",
"href": "{id}"
}, {
"rel": "up",
"href": "{upId}"
}]
}
}
And if a collection of instance resources were retrieved with JSON
representation:
GET /Resource/
[{
"id": "thing",
"upId": "parent"
}, {
"id": "thing2",
"upId": "parent"
}]
This would indicate that for the first item in the collection, its
URI as its own resource would resolve to "/Resource/thing" and the
first item's "up" relation SHOULD be resolved to the resource at
"/Resource/parent".
Note that these relationship values are case-insensitive, consistent
with their use in HTML and the HTTP Link header [RFC5988].
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6.4.1. Security Considerations for "self" links
When link relation of "self" is used to denote a full representation
of an object, the user agent SHOULD NOT consider the representation
to be the authoritative representation of the resource denoted by the
target URI if the target URI is not equivalent to or a sub-path of
the URI used to request the resource representation which contains
the target URI with the "self" link.
For example, if a hyper-schema was defined:
{
"links": [{
"rel": "self",
"href": "{id}"
}]
}
And a resource was requested from somesite.com:
GET /foo/
With a response of (with newlines and whitespace added):
Content-Type: application/json; profile="http://example.com/alpha"
[{
"id": "bar",
"name": "This representation can be safely treated
as authoritative "
}, {
"id": "/baz",
"name": "This representation should not be treated as
authoritative the user agent should make request the
resource from '/baz' to ensure it has the authoritative
representation"
}, {
"id": "http://othersite.com/something",
"name": "This representation
should also not be treated as authoritative and the
target resource representation should be retrieved
for the authoritative representation"
}]
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6.5. title
This property defines a title for the link. The value must be a
string.
User agents MAY use this title when presenting the link to the user.
6.6. targetSchema
This property provides a schema that is expected to describe the link
target's representation. Depending on the protocol, the schema may
or may not describe the response to any particular request sent to
the link. This property is advisory only.
6.6.1. "targetSchema" and HTTP
The relationship between a resource's representation and HTTP
requests and responses is determined by RFC 7231, section 4.3.1 -
"GET", section 4.3.4 "PUT", and section 3.1.4.2, "Content-Location"
[RFC7231]. In particular, "targetSchema" suggests what a client can
expect for the response to an HTTP GET or any response for which the
"Content-Location" header is equal to the request URI, and what a
client should send if it replaces the resource in an HTTP PUT
request. Per RFC 5789 [RFC5789], the request structure for an HTTP
PATCH is determined by the combination of "targetSchema" and the
request media type.
6.6.2. Security Considerations for "targetSchema"
This property has similar security concerns to that of "mediaType".
Clients MUST NOT use the value of this property to aid in the
interpretation of the data received in response to following the
link, as this leaves "safe" data open to re-interpretation.
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For example, suppose two programmers are having a discussion about
web security using a text-only message board. Here is some data from
that conversation, with a URI of:
http://forum.example.com/topics/152/comments/13
{
"topicId": 152,
"commentId": 13,
"from": {
"name": "Jane",
"id": 5
},
"to": {
"name": "Jason",
"id": 8
},
"message": "It's easy, just add some HTML like
this: <script>doSomethingEvil()</script>"
}
The message string was split over two lines for readability.
A third party might then provide the following Link Description
Object at another location:
{
"rel": "evil-attack",
"href": "http://forum.example.com/topics/152/comments/13",
"targetSchema": {
"properties": {
"message": {
"description": "Re-interpret `message` as HTML",
"media": {
"type": "text/html"
}
}
}
}
}
If the client used this "targetSchema" value when interpreting the
above data, then it might display the contents of "message" as HTML.
At this point, the JavaScript embedded in the message might be
executed (in the context of the "forum.example.com" domain).
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6.7. mediaType
The value of this property is advisory only, and represents the media
type RFC 2046 [RFC2046], that is expected to be returned when
fetching this resource. This property value MAY be a media range
instead, using the same pattern defined in RFC 7231, section 5.3.2 -
HTTP "Accept" header [RFC7231].
This property is analogous to the "type" property of <a> elements in
HTML (advisory content type), or the "type" parameter in the HTTP
Link header [RFC5988]. User agents MAY use this information to
inform the interface they present to the user before the link is
followed, but this information MUST NOT use this information in the
interpretation of the resulting data. When deciding how to interpret
data obtained through following this link, the behaviour of user
agents MUST be identical regardless of the value of the this
property.
If this property's value is specified, and the link's target is to be
obtained using any protocol that supports the HTTP/1.1 "Accept"
header RFC 7231, section 5.3.2 [RFC7231], then user agents MAY use
the value of this property to aid in the assembly of that header when
making the request to the server.
If this property's value is not specified, then the value should be
taken to be "application/json".
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For example, if a schema is defined:
{
"links": [{
"rel": "self",
"href": "/{id}/json"
}, {
"rel": "alternate",
"href": "/{id}/html",
"mediaType": "text/html"
}, {
"rel": "alternate",
"href": "/{id}/rss",
"mediaType": "application/rss+xml"
}, {
"rel": "icon",
"href": "{id}/icon",
"mediaType": "image/*"
}]
}
A suitable instance described by this schema would have four links
defined. The link with a "rel" value of "self" would have an
expected MIME type of "application/json" (the default). The two
links with a "rel" value of "alternate" specify the locations of HTML
and RSS versions of the current item. The link with a "rel" value of
"icon" links to an image, but does not specify the exact format.
A visual user agent displaying the item from the above example might
present a button representing an RSS feed, which when pressed passes
the target URI (calculated "href" value) to an view more suited to
displaying it, such as a news feed aggregator tab.
Note that presenting the link in the above manner, or passing the URI
to a news feed aggregator view does not constitute interpretation of
the data, but an interpretation of the link. The interpretation of
the data itself is performed by the news feed aggregator, which
SHOULD reject any data that would not have also been interpreted as a
news feed, had it been displayed in the main view.
6.7.1. Security concerns for "mediaType"
The "mediaType" property in link definitions defines the expected
format of the link's target. However, this is advisory only, and
MUST NOT be considered authoritative.
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When choosing how to interpret data, the type information provided by
the server (or inferred from the filename, or any other usual method)
MUST be the only consideration, and the "mediaType" property of the
link MUST NOT be used. User agents MAY use this information to
determine how they represent the link or where to display it (for
example hover-text, opening in a new tab). If user agents decide to
pass the link to an external program, they SHOULD first verify that
the data is of a type that would normally be passed to that external
program.
This is to guard against re-interpretation of "safe" data, similar to
the precautions for "targetSchema".
6.8. submissionEncType
If present, this property indicates the media type format the client
should use for the request payload described by "submissionSchema"
(Section 6.9).
Omitting this keyword has the same behavior as a value of
application/json.
Note that "submissionEncType" and "submissionSchema" are not
restricted to HTTP URIs.
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For example, this link indicates that if you want to send an email to
the author of the context resource, your client needs to ask for both
a plain text and an HTML representation.
{
"links": [{
"submissionEncType": "multipart/alternative; boundary=ab12",
"rel": "author",
"href": "mailto:someone@example.com{?subject}",
"hrefSchema": {
"type": "object",
"properties": {
"subject": { "type": "string" }
},
"required": ["subject"]
},
"submissionSchema": {
"type": "array",
"items": [
{
"type": "string",
"media": { "type": "text/plain; charset=utf8" }
},
{
"type": "string",
"media": { "type": "text/html" }
}
],
"minItems": 2
}
}]
}
6.9. submissionSchema
This property contains a schema which defines the acceptable
structure of the document to be encoded according to the
"submissionEncType" property and sent to the target resource for
processing. This can be viewed as describing the domain of the
processing function implemented by the target resource.
This is a separate concept from the "targetSchema" (Section 6.6)
property, which is describing the target information resource
(including for replacing the contents of the resource in a PUT
request), unlike "submissionSchema" which describes the user-
submitted request data to be evaluated by the resource.
"submissionSchema" is intended for use with requests that have
payloads that are not defined in terms of the target representation.
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Omitting "submissionSchema" or setting the entire schema to "false"
prevents any user agent data from being accepted.
7. References
7.1. Normative References
[RFC2045] Freed, N. and N. Borenstein, "Multipurpose Internet Mail
Extensions (MIME) Part One: Format of Internet Message
Bodies", RFC 2045, DOI 10.17487/RFC2045, November 1996,
<http://www.rfc-editor.org/info/rfc2045>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
[RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
Resource Identifier (URI): Generic Syntax", STD 66,
RFC 3986, DOI 10.17487/RFC3986, January 2005,
<http://www.rfc-editor.org/info/rfc3986>.
[RFC6570] Gregorio, J., Fielding, R., Hadley, M., Nottingham, M.,
and D. Orchard, "URI Template", RFC 6570,
DOI 10.17487/RFC6570, March 2012,
<http://www.rfc-editor.org/info/rfc6570>.
[json-schema]
Wright, A., "JSON Schema: A Media Type for Describing JSON
Documents", draft-wright-json-schema-00 (work in
progress), October 2016.
7.2. Informative References
[RFC2046] Freed, N. and N. Borenstein, "Multipurpose Internet Mail
Extensions (MIME) Part Two: Media Types", RFC 2046,
DOI 10.17487/RFC2046, November 1996,
<http://www.rfc-editor.org/info/rfc2046>.
[RFC5789] Dusseault, L. and J. Snell, "PATCH Method for HTTP",
RFC 5789, DOI 10.17487/RFC5789, March 2010,
<http://www.rfc-editor.org/info/rfc5789>.
[RFC5988] Nottingham, M., "Web Linking", RFC 5988,
DOI 10.17487/RFC5988, October 2010,
<http://www.rfc-editor.org/info/rfc5988>.
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[RFC7231] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
Protocol (HTTP/1.1): Semantics and Content", RFC 7231,
DOI 10.17487/RFC7231, June 2014,
<http://www.rfc-editor.org/info/rfc7231>.
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Appendix A. Acknowledgments
Thanks to Gary Court, Francis Galiegue, Kris Zyp, and Geraint Luff
for their work on the initial drafts of JSON Schema.
Thanks to Jason Desrosiers, Daniel Perrett, Erik Wilde, Ben Hutton,
Evgeny Poberezkin, Brad Bowman, Gowry Sankar, Donald Pipowitch, Dave
Finlay, and Denis Laxalde for their submissions and patches to the
document.
Appendix B. Change Log
[[CREF5: This section to be removed before leaving Internet-Draft
status.]]
draft-wright-json-schema-hyperschema-01
* Fixed examples
* Added "hrefSchema" for user input to "href" URI Templates
* Removed URI Template pre-processing
* Clarified how links and data submission work
* Clarified how validation keywords apply hyper-schema keywords
and links
* Clarified HTTP use with "targetSchema"
* Renamed "schema" to "submissionSchema"
* Renamed "encType" to "submissionEncType"
* Removed "method"
draft-wright-json-schema-hyperschema-00
* "rel" is now optional
* rel="self" no longer changes URI base
* Added "base" keyword to change instance URI base
* Removed "root" link relation
* Removed "create" link relation
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* Removed "full" link relation
* Removed "instances" link relation
* Removed special behavior for "describedBy" link relation
* Removed "pathStart" keyword
* Removed "fragmentResolution" keyword
* Updated references to JSON Pointer, HTML
* Changed behavior of "method" property to align with hypermedia
best current practices
draft-luff-json-hyper-schema-01
* Split from main specification.
Authors' Addresses
Austin Wright (editor)
EMail: aaa@bzfx.net
Henry Andrews (editor)
Cloudflare, Inc.
EMail: henry@cloudflare.com
Geraint Luff
Cambridge
UK
EMail: luffgd@gmail.com
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