Bug 25636

"WARNING: Consideration of this document has been Deferred by the XMPP Standards Foundation. Implementation of the protocol described herein is not recommended."... so I don't intend to consider XEP-0058. It doesn't seem to be the same thing requested for Skype anyway.

How does Skype actually represent these edits? The easiest thing I can think of would be to have a key in every message header indicating the message ID (message-token or the planned protocol-token), and a key in the replacement message's header 'supersedes' (or something) indicating which message to replace.

The idea of discarding the original message worries me, though: it seems as though this basically provides a way to make message history untrustworthy. We should probably specify that UIs should provide access to the old versions until/unless explicitly deleted.

(In reply to comment #1)
> "WARNING: Consideration of this document has been Deferred by the XMPP
> Standards Foundation. Implementation of the protocol described herein is not
> recommended."... so I don't intend to consider XEP-0058. It doesn't seem to be
> the same thing requested for Skype anyway.
> 
> How does Skype actually represent these edits?

IIRC, it changes properties for a message object.

> The idea of discarding the original message worries me, though: it seems as
> though this basically provides a way to make message history untrustworthy. We
> should probably specify that UIs should provide access to the old versions
> until/unless explicitly deleted.

I did not demand that old message versions be deleted, it should be the client's policy. The scheme with a 'supersedes' header looks good to me. (NB: surely there must be an e-mail RFC where we can lift the header name from).

(In reply to comment #2)
> I did not demand that old message versions be deleted, it should be the
> client's policy. The scheme with a 'supersedes' header looks good to me. (NB:
> surely there must be an e-mail RFC where we can lift the header name from).

http://tools.ietf.org/html/draft-ietf-mailext-new-fields-06 calls it Supersedes (and one MUST NOT spell it "Supercedes" ☺). It agrees with the above discussion about leaving what to with the superseded message up to UI policy. Also, it touches upon ethics:

> In general, it is
> not illegal or unethical to change your mind, rather, it shows your
> openness to new ideas and willingness to listen to the arguments of
> other people.

Sjoerd has noted in real life that, in iChat's dialect of link-local XMPP, typing notifications are sent along with the partially-composed text. We could represent these by repeatedly superseding previous versions of a message!

So here's a spec branch which just defines a 'supersedes' header. From the spec:

  supersedes (s – Protocol_Message_Token)

    If present, this message supersedes a previous message, identified
    by its protocol-token or message-token header. The user interface
    MAY, for example, choose to replace the superseded message with this
    message, or grey out the : superseded message.

    | Skype, for example, allows the user to amend messages they have
    | already sent (to correct typos, etc.).

I think this is fine for incoming messages; for outgoing messages we need to solve bug 28740 or have special cases in the UI.

review+ from me for the branch wjt/supersedes in its current state.

(In reply to comment #4)
> Sjoerd has noted in real life that, in iChat's dialect of link-local XMPP,
> typing notifications are sent along with the partially-composed text. We could
> represent these by repeatedly superseding previous versions of a message!

I wonder whether we could have some convention like:

* if a message part has 'truncated':True, and the message is superseded by one where the corresponding part is a superset, UIs SHOULD replace the earlier message silently

* if a message header has 'draft':True, UIs SHOULD indicate it as a partial message, and expect it to be superseded; if that message is superseded, UIs SHOULD replace the earlier message silently

(In reply to comment #6)
> review+ from me for the branch wjt/supersedes in its current state.
> 
> (In reply to comment #4)
> > Sjoerd has noted in real life that, in iChat's dialect of link-local XMPP,
> > typing notifications are sent along with the partially-composed text. We could
> > represent these by repeatedly superseding previous versions of a message!
> 
> I wonder whether we could have some convention like:
> 
> * if a message part has 'truncated':True, and the message is superseded by one
> where the corresponding part is a superset, UIs SHOULD replace the earlier
> message silently
> 
> * if a message header has 'draft':True, UIs SHOULD indicate it as a partial
> message, and expect it to be superseded; if that message is superseded, UIs
> SHOULD replace the earlier message silently

(Do we want to be able to *send* partially-composed text in typing notifications? If so, this comes back to the UI needing to know whether or not the CM supports particular headers.)

(In reply to comment #6)
> * if a message part has 'truncated':True, and the message is superseded by one
> where the corresponding part is a superset, UIs SHOULD replace the earlier
> message silently

So I don't know which protocol this would be for.

> * if a message header has 'draft':True, UIs SHOULD indicate it as a partial
> message, and expect it to be superseded; if that message is superseded, UIs
> SHOULD replace the earlier message silently

This makes sense for representing iChat's drafts.

(In reply to comment #8)
> (In reply to comment #6)
> > * if a message header has 'draft':True, UIs SHOULD indicate it as a partial
> > message, and expect it to be superseded; if that message is superseded, UIs
> > SHOULD replace the earlier message silently
> 
> This makes sense for representing iChat's drafts.

(Though we also need some way to represent the other party never actually sending the message. I guess that's just the CM emitting an empty message with supersedes set.)

((I should wait longer before hitting Submit.))

(In reply to comment #6)
> review+ from me for the branch wjt/supersedes in its current state.

Merged it. The remaining supersedes branch is just WIP for:

> * if a message part has 'truncated':True, and the message is superseded by one
> where the corresponding part is a superset, UIs SHOULD replace the earlier
> message silently
> 
> * if a message header has 'draft':True, UIs SHOULD indicate it as a partial
> message, and expect it to be superseded; if that message is superseded, UIs
> SHOULD replace the earlier message silently

No branch here, retitling.

Blocked by bug #28740 for sending, but not for receiving.

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