VCON for MIMI Messages

Syntax A MIMI conversation (or portion thereof) is represented in VCON with a mandatory list of parties and dialogs, a new top-level room object, and optionally attachment objects.

Room information This document adds a top-level room object. It contains metadata known about the room at the start of the VCON period.

id is the MIMI room ID URL. It is mandatory.
name is the textual name of the room. It is optional.

Parties The parties array MUST contain all the participants who were in the conversation at any point in time during the period represented by the VCON. This document adds a new party_object_type: imUri. It is mandatory. The name field is optional. The role indicates the MIMI role and is optional. The document also adds a thumbprint party_object_type, which is the JWK thumbprint of the public key of the party. If there are multiple parties (clients) with the same imUri then the thumbprint is required, otherwise it is optional.

Extensions to the dialog object The dialog object consists of an array of instant messages of type "text". The start time is set to the hub received timestamp when available. The duration is zero. The parties array consist of the party indexes of those who were active participants when the message was sent. The originator is set to the parties index of the sender of the message.

messageId is the base64url encoding of the MIMI content messageId. It is mandatory.
replaces is the base64url encoding of the MIMI content messageId of the message this message replaces. It is optional if empty.
topicId is the base64url encoding of the MIMI topicId. It is optional if empty.
expires is the expiration date/time of the message expressed as a VCON (text) date_type. It is optional if empty.
inReplyTo is an array of three values: the base64url encoding of the MIMI content messageId of the message to which this message is replying (or reacting), the hash algorithm expressed as an integer (SHA-256 is 1), and the base64url hash of the decrypted mimi-content. It is optional if empty.
lastSeen is an array of base64url-encoded message ids. It is mandatory.
mimiExtensions is a object (map) containing MIMI extensions. It is optional.

VCON typically expresses content using the body, encoding, and mimetype fields. In order to preserve this convention we use these fields directly for a MIMI SinglePart structure, but use new MultiPart and ExternalPart structure for those MIMI structures. For a SinglePart these two fields could be present.

disposition - optional if set to the default value ("render")
language - optional if absent

If there is only a single part its "partIndex" is 0.

MultiPart

partSemantics is one of "chooseOne", "singleUnit", or "processAll". It is mandatory.
parts is an array of Parts. It is mandatory.

Part

disposition - optional if set to the default value ("render")
language - optional if absent
partIndex is an unsigned integer. It is mandatory in a Part object.
cardinality is one of "nullpart", "single", "external", or "multi". mandatory.

if cardinality is "single" or "external", then body, encoding, and mimetype fields are included directly in the Part object.

ExternalPart

mimetype (contentType in MIMI). optional but recommended.
url is the URL of the content as a text string. mandatory
expires is a date_type (text) date. optional.
size is an integer number of octets. optional.
description is a text string. optional.
filename is a text string. optional.
cached is a boolean. It is mandatory if it is true, which means that a copy of the external content is available in a vcon attachment object (see {#attachments}).
contentHash is the base64url encoded string of the hash of the external content, prefixed with the name of the hash algorithm and a colon (for example "sha256:"). contentHash is optional unless the external content has been included in a vcon attachment object.

ExternalPart has several fields for the decryption of the referenced content. These can be omitted once the content has been downloaded, decrypted, verified, and included in the VCON attachments array. All of them are base64url encoded strings. Otherwise they are mandatory if present in the MIMI content.

encAlg
key
nonce
aad

Changes to the room Changes to the room metadata or participation should be accompanied by a new dialog type:

room metadata changes
participant identity change
participants joining and leaving
participants adding new clients
moderation events?

TODO add additional fields

party_event_type events When there is a change to the parties represented in a room, the party_event_type.event is added.

add: user added herself directly
welcome: user added by someone else
leave: user leaves of their own accord
remove: user is removed by another user
ban: user is banned from the group