Example Media Types for Use in Documentation
A reserved pretend media type, so documentation examples can never be mistaken for real requirements.
Taylor, T., "Example Media Types for Use in Documentation", RFC 4735, DOI 10.17487/RFC4735, October 2006, <https://www.rfc-editor.org/info/rfc4735>.
@misc{rfc4735,
series = {Request for Comments},
number = 4735,
howpublished = {RFC 4735},
publisher = {RFC Editor},
doi = {10.17487/RFC4735},
url = {https://www.rfc-editor.org/info/rfc4735},
author = {T. Taylor},
title = {{Example Media Types for Use in Documentation}},
pagetotal = 6,
year = 2006,
month = oct,
} RFC text
Contents
Network Working Group T. Taylor
Request for Comments: 4735 Nortel
Category: Standards Track October 2006
Example Media Types for Use in Documentation
Status of This Memo
This document specifies an Internet standards track protocol for the
Internet community, and requests discussion and suggestions for
improvements. Please refer to the current edition of the "Internet
Official Protocol Standards" (STD 1) for the standardization state
and status of this protocol. Distribution of this memo is unlimited.
Copyright Notice
Copyright (C) The Internet Society (2006).
Abstract
This document is registration for the 'example' media type and
'example' subtypes within the standards tree. The 'example/*' and
'*/example' media types are defined for documentation purposes only.
1. Introduction
From time to time, documents created by the IETF or by other
standards bodies show examples involving the use of media types,
where the actual media type is not relevant. It would be useful in
such cases to be able to show a media type whose illustrative role in
the example is clear. In the worst case, this can be useful to debug
implementations where the designer mistook the example for a
requirement of the protocol concerned.
To meet this need, this document registers the following media types:
o the 'example' media type;
o the 'application/example', 'audio/example', 'image/example',
'message/example', 'model/example', 'multipart/example',
'text/example', and 'video/example' media subtypes.
It is suggested that compilers of illustrative examples involving
media types in trees other than the standards tree might also
incorporate the string "example" into their hypothetical media types.
2. 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 [RFC2119].
3. Registration of the 'example' Media Type
This section registers the 'example' media type in accordance with
the requirements of RFC 4288.
Type name: example.
Subtype name: any subtype may be used with the 'example' type.
However, IANA MUST NOT register any subtypes for the 'example' media
type.
Required parameters: as invented by the user.
Optional parameters: as invented by the user.
Encoding considerations: as invented by the user.
Security considerations: The 'example' media type is defined for use
in documentation only. It MUST NOT be implemented. Its appearance
in real code could lead to unpredictable results and therefore open
up security holes.
Interoperability considerations: Any attempt to negotiate or send the
'example' media type is bound to lead to interoperability problems.
Published specification: this document.
Applications that use this media type: as invented by the user.
Additional information:
Magic number(s): not applicable.
File extension(s): not applicable.
Macintosh file type code(s): not applicable.
Person & email address to contact for further information:
ietf-types@iana.org.
Intended usage: LIMITED USE.
Restrictions on usage: This type is intended only for use in
documents providing examples involving specification of some media
type, where the actual media type used is irrelevant.
Author: Internet Engineering Task Force
Change controller: Internet Engineering Task Force
4. Registration of the 'application/example', 'audio/example',
'image/example', 'message/example', 'model/example',
'multipart/example', 'text/example', and 'video/example' Subtypes
This section registers 'example' media subtypes in accordance with
the requirements of RFC 4288.
Type name: 'application', 'audio', 'image', 'message', 'model',
'multipart', 'text', and 'video'.
Subtype name: 'example'.
Required parameters: those required by the type and any others as
invented by the user.
Optional parameters: those offered by the type and any others as
invented by the user.
Encoding considerations: as invented by the user.
Security considerations: The 'example' media subtypes are defined
for use in documentation only. They MUST NOT be implemented. Their
appearance in real code could lead to unpredictable results and
therefore open up security holes.
Interoperability considerations: Any attempt to negotiate or send
one of these 'example' media subtypes is bound to lead to
interoperability problems.
Published specification: this document.
Applications that use this media type: as invented by the user.
Additional information:
Magic number(s): not applicable.
File extension(s): not applicable.
Macintosh file type code(s): not applicable.
Person & email address to contact for further information:
ietf-types@iana.org.
Intended usage: LIMITED USE.
Restrictions on usage: These subtypes are intended only for use in
documents providing examples involving specification of some subtype
of the given media type, where the actual subtype used is irrelevant.
Author: Internet Engineering Task Force
Change controller: Internet Engineering Task Force
5. Security Considerations
The 'example' media type and subtypes are defined for use in
documentation only. They MUST NOT be implemented. Any attempt to
implement them in real code could lead to unpredictable results and
thus potentially open up security holes.
6. IANA Considerations
This document specifies and registers the 'example' media type and
the 'application/example', 'audio/example', 'image/example',
'message/example', 'model/example', 'multipart/example',
'text/example', and 'video/example' subtypes.
7. Acknowledgements
This document sprang from Magnus Westerland's expression of need and
Rod Walsh's support and suggestions for generalization. Warnings
against implementation in the Security Considerations and
Interoperability Considerations sections and the 'multipart/example'
subtype were added at John Klensin's suggestion. Some editing
touchups and strengthening of the language in the Security
Considerations section were done in response to the Gen-ART reviewer,
Sharon Chisholm.
8. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC4288] Freed, N. and J. Klensin, "Media Type Specifications and
Registration Procedures", BCP 13, RFC 4288, December 2005.
Author's Address
Tom Taylor
Nortel
1852 Lorraine Ave
Ottawa, Ontario K1H 6Z8
Canada
EMail: taylor@nortel.com
Full Copyright Statement
Copyright (C) The Internet Society (2006).
This document is subject to the rights, licenses and restrictions
contained in BCP 78, and except as set forth therein, the authors
retain all their rights.
This document and the information contained herein are provided on an
"AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
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Acknowledgement
Funding for the RFC Editor function is provided by the IETF
Administrative Support Activity (IASA).
AI ELI5
On this page
§1Why Examples Need a Safe Name
Documents from the IETF and other standards bodies sometimes show examples that involve a media type, where the actual type is not relevant. In those cases it helps to show a type whose illustrative role is clear.
The RFC notes that in the worst case this helps to debug implementations where the designer mistook the example for a requirement of the protocol concerned. It also suggests that people writing examples with media types in trees other than the standards tree might include the string example in their hypothetical types.
If a recipe says 'use flour type X' as a pretend example, a cook might think X is real. A silly, obviously pretend name stops that mix-up.
§2What Gets Registered
The RFC registers two things in the standards tree, following the rules of RFC 4288.
- The top-level
examplemedia type. - The subtype
exampleunder eight existing types:application,audio,image,message,model,multipart,textandvideo.
So text/example and video/example are valid placeholders when a document needs a text or video type, and example/* works when even the top-level type is irrelevant.
There is a pretend label for every kind of file the document mentions: pretend picture, pretend sound, pretend video, and so on.
- Standards tree
- example no subtypes may be registered
- application/example
- audio/example
- image/example
- message/example
- model/example
- multipart/example
- text/example
- video/example
§3Rules for the example Type
Any subtype may be used with the example type, but IANA MUST NOT register any subtypes for it. Its parameters and encoding considerations are 'as invented by the user', since nothing real is behind it.
The registration lists the intended usage as LIMITED USE. It is intended only for documents giving examples of specifying some media type where the actual type used is irrelevant. The author and change controller are the Internet Engineering Task Force.
The pretend label is yours to fill in however you like for a story, but the librarian is not allowed to add any real books under it.
§4Rules for the example Subtypes
For the eight */example subtypes, required parameters are those required by the type plus any others invented by the user. Optional parameters are those offered by the type plus any others invented by the user.
As with the top-level type, usage is LIMITED USE, meant only for documents giving examples of some subtype of the given media type, where the actual subtype is irrelevant.
Each pretend label follows the normal rules of its kind of file, and you may make up extra details for your story.
§5Do Not Implement These
The RFC is firm that the example type and subtypes are defined for documentation only. They MUST NOT be implemented. Their appearance in real code could lead to unpredictable results and thus potentially open up security holes.
On interoperability, any attempt to negotiate or send one of these types is bound to lead to interoperability problems.
A pretend label is for stories only. If a real machine starts using it, nobody can predict what will happen.
§6The IANA Registration
The document itself is the registration. It specifies and registers the example media type and the application/example, audio/example, image/example, message/example, model/example, multipart/example, text/example and video/example subtypes.
The contact address given for further information is ietf-types@iana.org.
The official list keeper wrote these pretend names down so that nobody else claims them for something real.