[Standards] XEP-184: Message Delivery Receipts - Message Type of Ack Messages

Florian Schmaus flo at geekplace.eu
Mon Apr 13 21:03:56 UTC 2015

On 13.04.2015 22:35, Christian Schudt wrote:
> Sounds good to me… except XEP-0045 still uses „MUST NOT“ for groupchat-type in private occupant-to-occupant messages.
> Might be inconsistent wording across the two specs.
> Furthermore I can understand the issue raised in your linked post [1]: In software an empty String and a null reference (here: with regards to <body>) are often treated similarly (C# even has String.IsNullOrEmpty()), leading to the issue described (displaying acks wrongly as empty chat messages).
> Such an issue can’t be prevented by „not making assumptions about the type“, when dealing with receipts.

An empty string is not a "null" String. Similar, it's a difference if a
message stanzas contains a body element containing the empty String, or
no body at all. This must simply be treated differently. And I guess
it's possible to do so in most (any?) programming languages out there.
Therefore I don't see why such "issue(s) can't be prevented".

It's very common in XMPP to send messages without a 'body' element. And
if your software behaves like this is a message with a body element
containing the empty string, then I consider this a bug in the your code.

> Having that in mind, are there any benefits to send acks as chat-messages (or to explicitly allow them to be sent by the specification)?

This is mostly motivated by not restricting things without a need.

- Florian

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