Network Working Group D. Crocker
Internet-Draft Brandenburg InternetWorking
Intended status: Experimental R. Signes
Expires: July 22, 2021 Fastmail
N. Freed
Oracle
January 18, 2021
React: Indicating Summary Reaction to a Message
draft-crocker-inreply-react-07
Abstract
The popularity of social media has led to user comfort with easily
signaling basic reactions to an author's posting, such as with a
'thumbs up' or 'smiley' graphic. This specification permits a
similar facility for Internet Mail.
Status of This Memo
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Reaction Content-Disposition . . . . . . . . . . . . . . . . 3
3. Reaction Message Processing . . . . . . . . . . . . . . . . . 4
4. Usability Considerations . . . . . . . . . . . . . . . . . . 5
4.1. Example Message . . . . . . . . . . . . . . . . . . . . . 5
4.2. Example Display . . . . . . . . . . . . . . . . . . . . . 6
5. Security Considerations . . . . . . . . . . . . . . . . . . . 6
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
7. Experimental Goals . . . . . . . . . . . . . . . . . . . . . 7
8. Normative References . . . . . . . . . . . . . . . . . . . . 7
Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 8
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8
1. Introduction
The popularity of social media has led to user comfort with easily
signaling summary reactions to an author's posting, by marking basic
emoji graphics, such as with a 'thumbs up', 'heart', or 'smiley'
indication. Sometimes the permitted repertoire is constrained to a
small set and sometimes a more extensive range of indicators is
supported.
This specification defines a similar facility for Internet Mail.
While it is already possible to include symbols and graphics as part
of an email reply's content, there has not been an established means
of signalling the semantic substance that such data are to be taken
as a summary 'reaction' to the original message. That is, a
mechanism to identify symbols as specifically providing a summary
reaction to the cited message, rather than merely being part of the
free text in the body of a response. Such a structured use of the
symbol(s) allows recipient MUAs to correlate this reaction to the
original message and possibly to display the information
distinctively.
This facility defines a new MIME Content-Disposition, to be used in
conjunction with the In-Reply-To header field, to specify that a part
of a message containing one or more emojis be treated as a summary
reaction to a previous message.
Unless provided here, terminology, architecture and specification
notation used in this document are incorporated from [Mail-Arch],
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[Mail-Fmt], [MIME], and [ABNF]. The ABNF rule Emoji-Seq is inherited
from [Emoji-Seq].
Normative language, per [RFC8174]:
In many IETF documents, several words, when they are in all
capitals as shown below, are used to signify the requirements in
the specification. These capitalized words can bring significant
clarity and consistency to documents because their meanings are
well defined. This document defines how those words are
interpreted in IETF documents when the words are in all capitals.
* These words can be used as defined here, but using them is not
required. Specifically, normative text does not require the
use of these key words. They are used for clarity and
consistency when that is what's wanted, but a lot of normative
text does not use them and is still normative.
* The words have the meanings specified herein only when they are
in all capitals.
* When these words are not capitalized, they have their normal
English meanings and are not affected by this document.
Authors who follow these guidelines should incorporate this phrase
near the beginning of their document:
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.
2. Reaction Content-Disposition
A message sent as a reply MAY include a part containing:
Content-Disposition: Reaction
If such a field is specified the content-type of the part MUST be:
Content-Type: text/plain; charset=utf-8
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The content of this part is restricted to single line of emoji. The
[ABNF] is:
part-content = emoji *(lwsp emoji) CRLF
emoji = emoji_sequence
emoji_sequence = { defined in [Emoji-Seq] }
base-emojis = thumbs-up / thumbs-down / grinning-face / frowning-face / crying-face
thumbs-up = {U+1F44D}
thumbs-down = {U+1F44E}
grinning-face = {U+1F600}
frowning-face = {U+2639}
crying-face = {U+1F622}
The rule emoji_sequence is inherited from [Emoji-Seq]. It permits
one or more bytes to form a single presentation image.
The rule base-emojis MAY be used as a simple, common list, or
'vocabulary' of emojis. It was developed from some existing
practice, in social networking, and is therefore intended for use.
However support for it is not required. Having providers and
consumers employ a common set will facilitate user interoperability,
but different sets of users might want to have different, common
(shared) sets.
The emoji(s) express a recipient's summary reaction to the specific
message referenced by the accompanying In-Reply-To header field.
[Mail-Fmt].
Reference to unallocated code points SHOULD NOT be treated as an
error; associated bytes SHOULD be processed using the system default
method for denoting an unallocated or undisplayable code point.
3. Reaction Message Processing
The presentation aspects of reaction processing are necessarily MUA-
specific and beyond the scope of this specification. In terms of the
message itself, a recipient MUA that supports this mechanism operates
as follows:
1. If a received message R contains an In-Reply-To: header-field,
check to see if it references a previous message the MUA has sent
or received.
2. If R's In-Reply-To: does reference one, then check R's message
content for a part with a "reaction" content-disposition at
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either the outermost level or as part of a multipart at the
outermost level.
3. If such a part is found, and the content of the part conforms to
the restrictions outlined above, remove the part from the message
and process the part as a reaction.
4. Processing terminates if no parts remain in the message. If
parts remain process the remaining message content as a reply.
Again, the handling of a message that has been successfully processed
is MUA-specific and beyond the scope of this specification.
4. Usability Considerations
This specification defines a mechanism for the structuring and
carriage of information. It does not define any user-level details
of use. However the design of the user-level mechanisms associated
with this facility is paramount. This section discusses some issues
to consider.
Creation: Because an email environment is different from a typical
social media platform, there are significant -- and potentially
challenging -- choices in the design of the user interface, to
support indication of a reaction. Is the reaction to be sent only
to the original author, or should it be sent to all recipients?
Should the reaction always be sent in a discrete message
containing only the reaction, or should the user also be able to
include other message content? (Note that carriage of the
reaction in a normal email message enables inclusion of this other
content.)
Display: Reaction indications might be more useful when displayed in
close visual proximity to the original message, rather than merely
as part of an email response thread. The handling of multiple
reactions, from the same person, is also an opportunity for
possibly-interesting user experience design choice.
4.1. Example Message
A simple message exchange might be:
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To: recipient@example.com
From: author@example.com
Date: Today, 29 February 2021 00:00:00 -800
Message-id: 12345@example.com
Subject: Meeting
Can we chat at 1pm pacific, today?
with a thumbs-up, affirmative response of:
To: author@example.com
From: recipient@example.com
Date: Today, 29 February 2021 00:00:10 -800
Message-id: 12345@example.com
Subject: Meeting
Mime-Version: 1.0 (1.0)
Content-Type: text/plain; charset=utf-8
Content-Disposition: Reaction
{U+1F44E}
It could, of course, be more elaborate, such as the first of a MIME
multipart sequence.
4.2. Example Display
Repeating the caution that actual use of this capability requires
careful usability design and testing, this section offers simple
examples -- which have not been tested -- of how the reaction
response might be displayed in a summary list of messages :
Summary: Summary listings of messages in a folder include columns
such as Subject, From, and Date. Another might be added, to show
common reactions and a count of how many of them have been
received.
Message: A complete message is often displayed with a tailored
section for header-fields, enhancing the format and showing only
selected header fields. It might include one for reactions, again
showing the symbol and a count.
5. Security Considerations
This specification employs message content that is a strict subset of
existing content, and thus introduces no new content-specific
security considerations. The fact that this content is structured
might seem to make it a new threat surface, but there is no analysis
demonstrating that it does.
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This specification defines a distinct label for specialized message
content. Processing that handles the content differently from other
content in the message body might introduce vulnerabilities.
6. IANA Considerations
The React MIME Content-Disposition parameter is registered, per
[RFC2183]
Content-Disposition parameter name: Reaction
Allowable values for this parameter: (none)
Description: Permit a recipient to respond by signaling basic
reactions to an author's posting, such as with a 'thumbs up' or
'smiley' graphic
7. Experimental Goals
The basic, email-specific mechanics for this capability are well-
established and well-understood. Points of concern, therefore, are
with market interest and with usability. So the questions to answer,
while the header field has experimental status are:
o Is there demonstrated interest by MUA developers?
o If MUA developers add this capability, is it used by authors?
o Does the presence of the Reaction capability create any
operational problems for recipients?
o Does the presence of the Reaction capability demonstrate
additional security issues?
8. Normative References
[ABNF] Crocker, D. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", RFC 5234, January 2008.
[Emoji-Seq]
Davis, M., Ed. and P. Edberg., Ed., "Unicode(R) Technical
Standard #51: Unicode Emoji", WEB
http://www.unicode.org/reports/tr51/#def_emoji_sequence,
September 2020.
[Mail-Arch]
Crocker, D., "Internet Mail Architecture", RFC 5598, July
2009.
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[Mail-Fmt]
Resnick, P., Ed., "Internet Message Format", RFC 5322,
October 2008.
[MIME] Freed, N. and N. Borenstein, "Multipurpose Internet Mail
Extensions (MIME) Part One: Format of Internet Message
Bodies", RFC 2045, November 1996.
[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/info/rfc2119>.
[RFC2183] Troost, R., Dorner, S., and K. Moore, Ed., "Communicating
Presentation Information in Internet Messages: The
Content-Disposition Header Field", RFC 2183,
DOI 10.17487/RFC2183, August 1997,
<https://www.rfc-editor.org/info/rfc2183>.
[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/info/rfc8174>.
Appendix A. Acknowledgements
This specification has had substantive commentary on the ietf-822,
dispatch, and last-call mailing lists. Active commentary and
suggestions were offered by: Nathaniel Borenstein, Richard Clayton,
Bron Gondwana, Nick Hilliard, Valdis Klētnieks, Eliot Lear,
Barry Leiba, John Levine, Brandon Long, Keith Moore, Pete Resnick,
Michael Richardson, Alessandro Vesely.
Authors' Addresses
Dave Crocker
Brandenburg InternetWorking
Email: dcrocker@bbiw.net
Ricardo Signes
Fastmail
Email: rjbs@semiotic.systems
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Ned Freed
Oracle
Email: ned.freed@mrochek.com
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