React: Indicating Summary Reaction to a Message

Internet-Draft	react	February 2021
Crocker, et al.	Expires 19 August 2021	[Page]

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

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 19 August 2021.¶

Copyright Notice

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 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.¶

1. Introduction

The popularity of social media has led to user comfort with easily signaling summary reactions to an author's posting, by using 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], [Mail-Fmt], [MIME], and [ABNF]. The ABNF rule Emoji-Seq is inherited from [Emoji-Seq].¶

Normative language, per [RFC8174]:¶

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

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 defines a set of octet sequences, each of which forms a single pictograph.¶

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 intended for similar use. However support for it as a base vocabulary 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, for the message in which they both are present. [Mail-Fmt]. For processing details, see Section 3.¶

Reference to unallocated code points SHOULD NOT be treated as an error; the corresponding octets 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:¶

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.¶
If R's In-Reply-To: does reference one, then check R's message content for a part with a "reaction" Content-Disposition header field, at either the outermost level or as part of a multipart at the outermost level.¶
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.¶
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:¶

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.org
Date: Today, 29 February 2021 00:00:10 -800
Message-id: 56789@example.org
In-Reply-To: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 add a field 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.¶

This specification defines a distinct Content-Disposition value, for specialized message content. Processing that handles the content differently from other content in the message body might introduce vulnerabilities.¶

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:¶

Is there demonstrated interest by MUA developers?¶
If MUA developers add this capability, is it used by authors?¶
Does the presence of the Reaction capability create any operational problems for recipients?¶
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, <https://www.rfc-editor.org/rfc/rfc5234>.
[Emoji-Seq]: Davis, M., Ed. and P. Edberg., Ed., "Unicode® Technical Standard #51: Unicode Emoji", WEB http://www.unicode.org/reports/tr51/#def_emoji_sequence, 18 September 2020.
[Mail-Arch]: Crocker, D., "Internet Mail Architecture", RFC 5598, July 2009, <https://www.rfc-editor.org/rfc/rfc5598>.
[Mail-Fmt]: Resnick, P., Ed., "Internet Message Format", RFC 5322, October 2008, <https://www.rfc-editor.org/rfc/rfc5322>.
[MIME]: Freed, N. and N. Borenstein, "Multipurpose Internet Mail Extensions (MIME) Part One: Format of Internet Message Bodies", RFC 2045, November 1996, <https://www.rfc-editor.org/rfc/rfc2045>.
[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>.