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Applications and Real-Time reaction emoji social networking email affect messaging emoticon smileys like mime reply 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.

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 , , , and . The ABNF rule Emoji-Seq is inherited from . Normative language, per : 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.

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 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 . 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. . For processing details, see . 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.

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.

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. 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.) 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.

A simple message exchange might be:

with a thumbs-up, affirmative response of:

It could, of course, be more elaborate, such as the first of a MIME multipart sequence.

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 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. 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.

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.

The IANA is request to register the React MIME Content-Disposition parameter, per React (none) Permit a recipient to respond by signaling basic reactions to an author's posting, such as with a 'thumbs up' or 'smiley' graphic

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?

In many standards track documents several words are used to signify the requirements in the specification. These words are often capitalized. This document defines these words as they should be interpreted in IETF documents. This document specifies an Internet Best Current Practices for the Internet Community, and requests discussion and suggestions for improvements. This memo provides a mechanism whereby messages conforming to the MIME specifications [RFC 2045, RFC 2046, RFC 2047, RFC 2048, RFC 2049] can convey presentational information. It specifies the "Content- Disposition" header field, which is optional and valid for any MIME entity ("message" or "body part"). [STANDARDS-TRACK] Brandenburg InternetWorking THUS plc Google, Inc. Apple, Inc Qualcomm Incorporated Brandenburg InternetWorking Innosoft First Virtual RFC 2119 specifies common key words that may be used in protocol specifications. This document aims to reduce the ambiguity by clarifying that only UPPERCASE usage of the key words have the defined special meanings.

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, Kjetil Torgrim Homme, Barry Leiba, Valdis Klētnieks, Eliot Lear, Barry Leiba, John Levine, Brandon Long, Keith Moore, Pete Resnick, Michael Richardson, Alessandro Vesely.