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HTTPAPI                                                         R. Polli
Internet-Draft     Digital Transformation Department, Italian Government
Intended status: Informational                              7 March 2022
Expires: 8 September 2022


                          REST API Media Types
               draft-ietf-httpapi-rest-api-mediatypes-01

Abstract

   This document registers the following media types used in APIs on the
   IANA Media Types registry: application/yaml, application/schema+json,
   application/schema-instance+json, application/openapi+json, and
   application/openapi+yaml.

Note to Readers

   _RFC EDITOR: please remove this section before publication_

   Discussion of this draft takes place on the HTTP APIs working group
   mailing list (httpapi@ietf.org), which is archived at
   https://mailarchive.ietf.org/arch/browse/httpapi/
   (https://mailarchive.ietf.org/arch/browse/httpapi/).

   The source code and issues list for this draft can be found at
   https://github.com/ietf-wg-httpapi/mediatypes (https://github.com/
   ietf-wg-httpapi/mediatypes).

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 https://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 8 September 2022.






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Copyright Notice

   Copyright (c) 2022 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 (https://trustee.ietf.org/
   license-info) in effect on the date of publication of this document.
   Please review these documents carefully, as they describe your rights
   and restrictions with respect to this document.  Code Components
   extracted from this document must include Revised BSD License text as
   described in Section 4.e of the Trust Legal Provisions and are
   provided without warranty as described in the Revised BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
     1.1.  Notational Conventions  . . . . . . . . . . . . . . . . .   3
   2.  Media Type registrations  . . . . . . . . . . . . . . . . . .   3
     2.1.  Media Type application/yaml . . . . . . . . . . . . . . .   3
     2.2.  The +yaml Structured Syntax Suffix  . . . . . . . . . . .   4
     2.3.  The OpenAPI Media Types . . . . . . . . . . . . . . . . .   5
       2.3.1.  Media Type application/openapi+json . . . . . . . . .   6
       2.3.2.  Media Type application/openapi+yaml . . . . . . . . .   7
     2.4.  JSON Schema Media Types . . . . . . . . . . . . . . . . .   8
       2.4.1.  The "$schema" Keyword . . . . . . . . . . . . . . . .   8
       2.4.2.  Identifying a Schema via a Media Type Parameter . . .   9
       2.4.3.  Linking to a Schema . . . . . . . . . . . . . . . . .  10
       2.4.4.  Fragment Identifiers  . . . . . . . . . . . . . . . .  10
       2.4.5.  Media Type application/schema+json  . . . . . . . . .  11
       2.4.6.  Media Type application/schema-instance+json . . . . .  12
   3.  Interoperability Considerations . . . . . . . . . . . . . . .  13
     3.1.  YAML Media Types  . . . . . . . . . . . . . . . . . . . .  13
       3.1.1.  YAML is an Evolving Language  . . . . . . . . . . . .  13
       3.1.2.  YAML and JSON . . . . . . . . . . . . . . . . . . . .  13
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .  15
     4.1.  YAML Media Types  . . . . . . . . . . . . . . . . . . . .  15
       4.1.1.  Arbitrary Code Execution  . . . . . . . . . . . . . .  15
       4.1.2.  Resource exhaustion . . . . . . . . . . . . . . . . .  15
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  16
   6.  Normative References  . . . . . . . . . . . . . . . . . . . .  16
   Appendix A.  Acknowledgements . . . . . . . . . . . . . . . . . .  18
   FAQ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  18
   Change Log  . . . . . . . . . . . . . . . . . . . . . . . . . . .  18
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .  18






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1.  Introduction

   OpenAPI Specification [oas] version 3 and above is a consolidated
   standard for describing HTTP APIs using the JSON [JSON] and YAML
   [YAML] data format.

   To increase interoperability when processing API specifications and
   leverage content negotiation mechanisms when exchanging OpenAPI
   Specification resources this specification register the following
   media-types: application/yaml, application/schema+json, application/
   schema-instance+json, application/openapi+json and application/
   openapi+yaml.

   Moreover it defines and registers the +yaml structured syntax suffix.

1.1.  Notational Conventions

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in
   BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.  These words may also appear in this
   document in lower case as plain English words, absent their normative
   meanings.

   This document uses the Augmented BNF defined in [RFC5234] and updated
   by [RFC7405].

   The terms "content", "content negotiation", "resource", and "user
   agent" in this document are to be interpreted as in [SEMANTICS].

2.  Media Type registrations

   This section describes the information required to register the above
   media types according to [MEDIATYPE]

2.1.  Media Type application/yaml

   The following information serves as the registration form for the
   application/yaml media type.

   Type name: application

   Subtype name: yaml

   Required parameters: None

   Optional parameters: None; unrecognized parameters should be ignored



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   Encoding considerations: Same as [JSON]

   Security considerations: see Section 4 of this document

   Interoperability considerations: see Section 3.1 of this document

   Published specification: (this document)

   Applications that use this media type: HTTP

   Fragment identifier considerations: Same as for application/json
   [JSON]

   Additional information:

   Deprecated alias names for this type: application/x-yaml, text/yaml,
   text/x-yaml

   Magic number(s): n/a

   File extension(s): yaml, yml

   Macintosh file type code(s): n/a

   Person and email address to contact for further information: See
   Authors' Addresses section.

   Intended usage: COMMON

   Restrictions on usage: None.

   Author: See Authors' Addresses section.

   Change controller: n/a

2.2.  The +yaml Structured Syntax Suffix

   The suffix +yaml MAY be used with any media type whose representation
   follows that established for application/yaml.  The media type
   structured syntax suffix registration form follows.  See [MEDIATYPE]
   for definitions of each of the registration form headings.

   Name: YAML Ain't Markup LanguageML (YAML)

   +suffix: +yaml

   References: [YAML]




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   Encoding considerations: see Section 2.1

   Fragment identifier considerations:

     The syntax and semantics of fragment identifiers specified for
     +yaml SHOULD be as specified for {{application-yaml}}

     The syntax and semantics for fragment identifiers for a specific
     `xxx/yyy+json` SHOULD be processed as follows:

     For cases defined in +yaml, where the fragment identifier resolves
     per the +yaml rules, then process as specified in +yaml.

        For cases defined in +yaml, where the fragment identifier does
        not resolve per the +yaml rules, then process as specified in
        `xxx/yyy+yaml`.

        For cases not defined in +yaml, then process as specified in
        `xxx/yyy+yaml`.

   Interoperability considerations: See Section 2.1

   Security considerations: See Section 2.1

   Contact: See Authors' Addresses section.

   Author: See Authors' Addresses section

   Change controller: n/a

2.3.  The OpenAPI Media Types

   The OpenAPI Specification Media Types convey OpenAPI document (OAS)
   files as defined in [oas] for version 3.0.0 and above.

   Those files can be serialized in [JSON] or [YAML].  Since there are
   multiple OpenAPI Specification versions, those media-types support
   the version parameter.

   The following examples conveys the desire of a client to receive an
   OpenAPI Specification resource preferably in the following order:

   1.  openapi 3.1 in YAML

   2.  openapi 3.0 in YAML

   3.  any openapi version in json




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   Accept: application/openapi+yaml;version=3.1,
           application/openapi+yaml;version=3.0;q=0.5,
           application/openapi+json;q=0.3

2.3.1.  Media Type application/openapi+json

   The following information serves as the registration form for the
   application/openapi+json media type.

   Type name: application

   Subtype name: openapi+json

   Required parameters: None

   Optional parameters: version; unrecognized parameters should be
   ignored

   Encoding considerations: Same as [JSON]

   Security considerations: see Section 4 of this document

   Interoperability considerations: None

   Published specification: (this document)

   Applications that use this media type: HTTP

   Fragment identifier considerations: Same as for application/json
   [JSON]

   Additional information:

   Deprecated alias names for this type: n/a

   Magic number(s): n/a

   File extension(s): json

   Macintosh file type code(s): n/a

   Person and email address to contact for further information: See
   Authors' Addresses section.

   Intended usage: COMMON

   Restrictions on usage: None.




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   Author: See Authors' Addresses section.

   Change controller: n/a

2.3.2.  Media Type application/openapi+yaml

   The following information serves as the registration form for the
   application/openapi+yaml media type.

   Type name: application

   Subtype name: openapi+yaml

   Required parameters: None

   Optional parameters: version; unrecognized parameters should be
   ignored

   Encoding considerations: Same as [JSON]

   Security considerations: see Section 4 of this document

   Interoperability considerations: see Section 2.1

   Published specification: (this document)

   Applications that use this media type: HTTP

   Fragment identifier considerations: Same as for application/json
   [JSON]

   Additional information:

   Deprecated alias names for this type: n/a

   Magic number(s): n/a

   File extension(s): yaml, yml

   Macintosh file type code(s): n/a

   Person and email address to contact for further information: See
   Authors' Addresses section

   Intended usage: COMMON

   Restrictions on usage: None.




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   Author: See Authors' Addresses section

   Change controller: n/a

2.4.  JSON Schema Media Types

   JSON Schema is a declarative domain-specific language for validating
   and annotating JSON documents (see [jsonschema]).

   This document registers the media types associated with JSON Schema.

   There are many dialects of JSON Schema in wide use today.  The JSON
   Schema maintainers have released several dialects including draft-04,
   draft-07, and draft 2020-12.  There are also several third-party JSON
   Schema dialects in wide use including the ones defined for use in
   OpenAPI and MongoDB.

   This specification defines little more than how to identify the
   dialect while leaving most of the semantics of the schema up to the
   dialect to define.  Clients MUST use the following order of
   precedence for determining the dialect of a schema.

   *  The $schema keyword (Section 2.4.1)

   *  The "schema" media type parameter (Section 2.4.2)

   *  The context of the enclosing document.  This applies only when a
      schema is embedded within a document.  The enclosing document
      could be another schema in the case of a bundled schema or it
      could be another type of document that includes schemas such as an
      OpenAPI document.

   *  If none of the above result in identifying the dialect, client
      behavior is undefined.

2.4.1.  The "$schema" Keyword

   The $schema keyword is used as a JSON Schema dialect identifier.  The
   value of this keyword MUST be a URI [RFC3986].  This URI SHOULD
   identify a meta-schema that can be used to validate that the schema
   is syntactically correct according to the dialect the URI identifies.

   The dialect SHOULD define where the $schema keyword is allowed and/or
   recognized in a schema, but it is RECOMMENDED that dialects do not
   allow the schema to change within the same Schema Resource.






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2.4.2.  Identifying a Schema via a Media Type Parameter

   Media types MAY allow for a schema media type parameter, to support
   content negotiation based on schema identifier (see Section 12 of
   [SEMANTICS]).  The schema media type parameter MUST be a URI-
   reference [RFC3986].

   The schema parameter identifies a schema that provides semantic
   information about the resource the media type represents.  When using
   the application/schema+json media type, the schema parameter
   identifies the dialect of the schema the media type represents.

   The schema URI is opaque and SHOULD NOT automatically be
   dereferenced.  Since schema doesn't necessarily point to a network
   location, the "describedby" relation is used for linking to a
   downloadable schema.

   The following is an example of content negotiation where a user agent
   can accept two different versions of a "pet" resource.  Each resource
   version is identified by a unique JSON Schema.

   Request:

   NOTE: '\' line wrapping per RFC 8792

   GET /pet/1234 HTTP/1.1
   Host: foo.example
   Accept: \
     application/schema-instance+json; schema="/schemas/v2/pet"; q=0.2, \
     application/schema-instance+json; schema="/schemas/v1/pet"; q=0.1

   Response:

   NOTE: '\' line wrapping per RFC 8792

   HTTP/1.1 200 Ok
   Content-Type: \
     application/schema-instance+json; schema="/schemas/v2/pet"

   {
     "petId": "1234",
     "name": "Pluto",
     ...
   }

   In the following example, the user agent is able to accept two
   possible dialects of JSON Schema and the server replies with the
   latest one.



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   Request:

   NOTE: '\' line wrapping per RFC 8792

   GET /schemas/v2/pet HTTP/1.1
   Host: foo.example
   Accept: application/schema+json; \
               schema="https://json-schema.org/draft/2020-12/schema", \
           application/schema+json; \
               schema="http://json-schema.org/draft-07/schema#"

   Response:

   NOTE: '\' line wrapping per RFC 8792

   HTTP/1.1 200 OK
   Content-Type: \
     application/schema+json; \
         schema="https://json-schema.org/draft/2020-12/schema"

   {
     "$id": "https://json-schema.org/draft/2020-12/schema",
     "$schema": "https://json-schema.org/draft/2020-12/schema",
     ...
   }

2.4.3.  Linking to a Schema

   It is RECOMMENDED that instances described by a schema provide a link
   to a downloadable JSON Schema using the link relation describedby, as
   defined by Linked Data Protocol 1.0, section 8.1
   [W3C.REC-ldp-20150226].

   In HTTP, such links can be attached to any response using the Link
   header [LINK].

   Link: <https://example.com/my-hyper-schema#>; rel="describedby"

2.4.4.  Fragment Identifiers

   Two fragment identifier structures are supported: JSON Pointers and
   plain-names.

   The use of JSON Pointers as URI fragment identifiers is described in
   [RFC6901].  Fragment identifiers that are empty or start with a /,
   MUST be interpreted as JSON Pointer fragment identifiers.





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   Plain-name fragment identifiers reference locally named locations in
   the document.  The dialect determines how plain-name identifiers map
   to locations within the document.  All fragment identifiers that do
   not match the JSON Pointer syntax MUST be interpreted as plain name
   fragment identifiers.

2.4.5.  Media Type application/schema+json

   The application/schema+json media type represents JSON Schema.  This
   schema can be an official dialect or a third-party dialect.  The
   following information serves as the registration form for the
   application/schema+json media type.

   *Type name*: application

   *Subtype name*: schema+json

   *Required parameters*: N/A

   *Optional parameters*:

   *  *schema*: A URI identifying the JSON Schema dialect the schema was
      written for.  If this value conflicts with the value of the
      $schema keyword in the schema, the $schema keyword takes
      precedence.

   *Encoding considerations*: Same as [JSON]

   *Security considerations*: See the "Security Considerations" section
   of [jsonschema]

   *Interoperability considerations*: See the "General Considerations"
   section of [jsonschema]

   *Published specification*: (this document)

   *Applications that use this media type*: JSON Schema is used in a
   variety of applications including API servers and clients that
   validate JSON requests and responses, IDEs that valid configuration
   files, databases that store JSON, and more.

   *Fragment identifier considerations*: See Section 2.4.4

   *Additional information*:

   *  *Deprecated alias names for this type*: N/A

   *  *Magic number(s)*: N/A



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   *  *File extension(s)*: json, schema.json

   *  *Macintosh file type code(s)*: N/A

   *Person and email address to contact for further information*: See
   Authors' Addresses section.

   *Intended usage*: COMMON

   *Restrictions on usage*: N/A.

   *Author*: See Authors' Addresses section.

   *Change controller*: N/A

2.4.6.  Media Type application/schema-instance+json

   The application/schema-instance+json media type is an extension of
   the [JSON] media type that just adds the schema media type parameter
   and fragment identification.  The following information serves as the
   registration form for the application/schema-instance+json media
   type.

   *Type name*: application

   *Subtype name*: schema-instance+json

   *Required parameters*: N/A

   *Optional parameters*:

   *  *schema*: A URI identifying a JSON Schema that provides semantic
      information about this JSON representation.

   *Encoding considerations*: Same as [JSON]

   *Security considerations*: Same as [JSON]

   *Interoperability considerations*: Same as [JSON]

   *Published specification*: (this document)

   *Applications that use this media type*: JSON Schema is used in a
   variety of applications including API servers and clients that
   validate JSON requests and responses, IDEs that valid configuration
   files, databases that store JSON, and more.

   *Fragment identifier considerations*: See Section 2.4.4



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   *Additional information*:

   *  *Deprecated alias names for this type*: N/A

   *  *Magic number(s)*: N/A

   *  *File extension(s)*: json

   *  *Macintosh file type code(s)*: N/A

   *Person and email address to contact for further information*: See
   Authors' Addresses section.

   *Intended usage*: COMMON

   *Restrictions on usage*: N/A

   *Author*: See Authors' Addresses section.

   *Change controller*: N/A

3.  Interoperability Considerations

3.1.  YAML Media Types

3.1.1.  YAML is an Evolving Language

   YAML is an evolving language and, in time, some features have been
   added, and others removed.

   While this document is based on a given YAML version [YAML], media
   types registration does not imply a specific version.  This allows
   content negotiation of version-independent YAML resources.

   Implementers concerned about features related to a specific YAML
   version can specify it in the documents using the %YAML directive
   (see Section 6.8.1 of [YAML]).

3.1.2.  YAML and JSON

   When using flow collection styles (see Section 7.4 of [YAML]) a YAML
   document could look like JSON [JSON], thus similar interoperability
   considerations apply.

   When using YAML as a more efficient format to serialize information
   intented to be consumed as JSON, information can be discarded: this
   includes comments (see Section 3.2.3.3 of [YAML]) and alias nodes
   (see Section 7.1 of [YAML]), that do not have a JSON counterpart.



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   # This comment will be lost
   # when serializing in JSON.
   Title:
     type: string
     maxLength: &text_limit 64

   Name:
     type: string
     maxLength: *text_limit  # Replaced by the value 64.

          Figure 1: JSON replaces alias nodes with static values.

   Implementers need to ensure that relevant information will not be
   lost during the processing.  For example, they might consider
   acceptable that alias nodes are replaced by static values.

   In some cases an implementer may want to define a list of allowed
   YAML features, taking into account that the following ones might have
   interoperability issues with JSON:

   *  non UTF-8 encoding, since YAML supports UTF-16 and UTF-32 in
      addition to UTF-8;

   *  mapping keys that are not strings;

   *  circular references represented using anchor (see Section 4.1.2
      and Figure 3).

   *  .inf and .nan float values, since JSON does not support them;

   *  non-JSON types, including the ones associated to tags like
      !!timestamp that were deployed in older YAML versions;

   *  tags in general, and specifically ones that do not map to JSON
      types like custom and local tags such as !!python/object and
      !mytag (see Section 2.4 of [YAML]);

   non-json-keys:
     2020-01-01: a timestamp
     [0, 1]: a sequence
     ? {k: v}
     : a map
   non-json-value: 2020-01-01

          Figure 2: Example of mapping keys not supported in JSON






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4.  Security Considerations

   Security requirements for both media type and media type suffix
   registrations are discussed in Section 4.6 of [MEDIATYPE].

4.1.  YAML Media Types

4.1.1.  Arbitrary Code Execution

   Care should be used when using YAML tags, because their
   implementation might trigger unexpected code execution.

   Code execution in deserializers should be disabled by default, and
   only be enabled explicitly.  In those cases, the implementation
   should ensure - for example, via specific functions - that the code
   execution results in strictly bounded time/memory limits.

   Many implementations provide safe deserializers addressing these
   issues.

4.1.2.  Resource exhaustion

   YAML documents are rooted, connected, directed graphs and can contain
   reference cycles, so they can't be treated as simple trees (see
   Section 3.2.1 of [YAML]).  An implementation that attempts to do that
   can infinite-loop at some point (e.g. when trying to serialize a YAML
   document in JSON).

   x: &x
     y: *x

                        Figure 3: A cyclic document

   Even if a document is not cyclic, treating it as a tree could lead to
   improper behaviors (such as the "billion laughs" problem).

   x1: &a1 ["a", "a"]
   x2: &a2 [*a1, *a1]
   x3: &a3 [*a2, *a2]

                    Figure 4: A billion laughs document

   This can be addressed using processors limiting the anchor recursion
   depth and validating the input before processing it; even in these
   cases it is important to carefully test the implementation you are
   going to use.  The same considerations apply when serializing a YAML
   representation graph in a format that do not support reference cycles
   (see Section 3.1.2).



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5.  IANA Considerations

   This specification defines the following new Internet media types
   [MEDIATYPE].

   IANA has updated the "Media Types" registry at
   https://www.iana.org/assignments/media-types
   (https://www.iana.org/assignments/media-types) with the registration
   information provided below.

      +==================================+==========================+
      | Media Type                       | Section                  |
      +==================================+==========================+
      | application/yaml                 | Section 2.1 of ThisRFC   |
      +----------------------------------+--------------------------+
      | application/openapi+yaml         | Section 2.3.2 of ThisRFC |
      +----------------------------------+--------------------------+
      | application/openapi+json         | Section 2.3.1 of ThisRFC |
      +----------------------------------+--------------------------+
      | application/schema+json          | Section 2.4.5 of ThisRFC |
      +----------------------------------+--------------------------+
      | application/schema-instance+json | Section 2.4.6 of ThisRFC |
      +----------------------------------+--------------------------+

                                  Table 1

   IANA has updated the "Structured Syntax Suffixes" registry at
   https://www.iana.org/assignments/media-type-structured-suffix
   (https://www.iana.org/assignments/media-type-structured-suffix) with
   the registration information provided below.

                    +========+========================+
                    | Suffix | Section                |
                    +========+========================+
                    | +yaml  | Section 2.2 of ThisRFC |
                    +--------+------------------------+

                                  Table 2

6.  Normative References

   [JSON]     Bray, T., Ed., "The JavaScript Object Notation (JSON) Data
              Interchange Format", STD 90, RFC 8259,
              DOI 10.17487/RFC8259, December 2017,
              <https://www.rfc-editor.org/rfc/rfc8259>.






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   [jsonschema]
              Wright, A., Andrews, H., Hutton, B., and G. Dennis, "JSON
              Schema Core", 28 January 2020,
              <https://json-schema.org/specification.html>.

   [LINK]     Nottingham, M., "Web Linking", RFC 8288,
              DOI 10.17487/RFC8288, October 2017,
              <https://www.rfc-editor.org/rfc/rfc8288>.

   [MEDIATYPE]
              Freed, N., Klensin, J., and T. Hansen, "Media Type
              Specifications and Registration Procedures", BCP 13,
              RFC 6838, DOI 10.17487/RFC6838, January 2013,
              <https://www.rfc-editor.org/rfc/rfc6838>.

   [oas]      Darrel Miller, Jeremy Whitlock, Marsh Gardiner, Mike
              Ralphson, Ron Ratovsky, and Uri Sarid, "OpenAPI
              Specification 3.0.0", 26 July 2017.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/rfc/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,
              <https://www.rfc-editor.org/rfc/rfc3986>.

   [RFC5234]  Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
              Specifications: ABNF", STD 68, RFC 5234,
              DOI 10.17487/RFC5234, January 2008,
              <https://www.rfc-editor.org/rfc/rfc5234>.

   [RFC6901]  Bryan, P., Ed., Zyp, K., and M. Nottingham, Ed.,
              "JavaScript Object Notation (JSON) Pointer", RFC 6901,
              DOI 10.17487/RFC6901, April 2013,
              <https://www.rfc-editor.org/rfc/rfc6901>.

   [RFC7405]  Kyzivat, P., "Case-Sensitive String Support in ABNF",
              RFC 7405, DOI 10.17487/RFC7405, December 2014,
              <https://www.rfc-editor.org/rfc/rfc7405>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/rfc/rfc8174>.





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Internet-Draft            REST API Media Types                March 2022


   [SEMANTICS]
              Fielding, R. T., Nottingham, M., and J. Reschke, "HTTP
              Semantics", Work in Progress, Internet-Draft, draft-ietf-
              httpbis-semantics-19, 12 September 2021,
              <https://datatracker.ietf.org/doc/html/draft-ietf-httpbis-
              semantics-19>.

   [W3C.REC-ldp-20150226]
              Speicher, S., Arwe, J., and A. Malhotra, "Linked Data
              Platform 1.0", World Wide Web Consortium Recommendation
              REC-ldp-20150226, 26 February 2015,
              <https://www.w3.org/TR/2015/REC-ldp-20150226>.

   [YAML]     Oren Ben-Kiki, Clark Evans, and Ingy dot Net, "YAML Ain't
              Markup Language Version 1.2", 1 October 2021,
              <https://yaml.org/spec/1.2/spec.html>.

Appendix A.  Acknowledgements

   Thanks to Erik Wilde and David Biesack for being the initial
   contributors of this specification, and to Darrel Miller and Rich
   Salz for their support during the adoption phase.

   In addition to the people above, this document owes a lot to the
   extensive discussion inside and outside the HTTPAPI workgroup.  The
   following contributors have helped improve this specification by
   opening pull requests, reporting bugs, asking smart questions,
   drafting or reviewing text, and evaluating open issues:

   Eemeli Aro, Tina (tinita) Mueller, Ben Hutton and Jason Desrosiers.

FAQ

   Q: Why this document?  After all these years, we still lack a proper
      media-type for YAML.  This has some security implications too (eg.
      wrt on identifying parsers or treat downloads)

Change Log

   RFC EDITOR PLEASE DELETE THIS SECTION.

Author's Address

   Roberto Polli
   Digital Transformation Department, Italian Government
   Italy
   Email: robipolli@gmail.com




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