Currently, the only activity metric available to entities considering interacting with a Multi-User Chat (XEP-0045) [1] chat is the number of occupants which is published in the Service Discovery (XEP-0030) [2] response.
However, the number of occupants alone is not a great metric for usefulness of a chat. On the one end of the spectrum there may be highly active, but small, groups of experts on a specific topic who are happy to help. On the other end of the spectrum there may be huge chats consisting mostly of lurkers.
This specification introduces a new field in the disco#info data which gives an indication of the rate at which messages are sent in a given group chat.
To request the current level of message activity, an entity sends a standard Service Discovery (XEP-0030) [2] information request to a MUC's address:
<iq from='hag66@shakespeare.lit/pda'
id='lx09df27'
to='coven@chat.shakespeare.lit'
type='get'>
<query xmlns='http://jabber.org/protocol/disco#info'/>
</iq>
Services implementing this specification MUST return the {urn:xmpp:muc-activity}message-activity field, if:
The field MUST contain an approximation of the number of messages sent per hour in this room as floating point value. For example approximation approaches, see the Implementation Notes below.
<iq from='coven@chat.shakespeare.lit'
id='lx09df27'
to='hag66@shakespeare.lit/pda'
type='result'>
<query xmlns='http://jabber.org/protocol/disco#info'>
<!-- ... -->
<x xmlns='jabber:x:data' type='result'>
<field var='FORM_TYPE' type='hidden'>
<value>http://jabber.org/protocol/muc#roominfo</value>
</field>
<!-- ... -->
<field var='{urn:xmpp:muc-activity}message-activity'
label='Messages per hour'>
<value>23.42</value>
</field>
</x>
</query>
</iq>
In particular, services MUST omit the field entirely if the above preconditions are not met. Services MUST NOT put placeholder values in the field.
The obvious "correct" implemetation to provide the message rate would be to, internally, query the number of messages sent in the room since its inception and divide that by the number of hours since its inception. Such an implementation is likely to be expensive, in particular for large, high-traffic rooms.
In order to cater for that, the Business Rules allow for some significant leeway in how implementations approximate the number of messages per hour.
For implementations where fetching the number of messages in a certain time frame is too expensive, the following simplified approach is outlined: For each MUC, allocate a shift register of 25 counters. Whenever an eligible message is broadcast through the MUC, increase the first counter. Every hour, shift the counters onward (so that the first counter becomes the second and so on) and reset the first counter to zero. Whenever the message rate is requested (via disco#info or otherwise), sum the counters two through 25 and divide the sum by 24.
That way, only constant storage per MUC and constant CPU time per message and request is required. As a trade-off, this introduces a latency of one hour for updating the counter.
This specification does not introduce new user interaction concepts.
Services MAY translate the label attribute of the field according to the language indicated in the requester's IQ stanza.
Services MUST choose a sufficiently cheap algorithm to provide the message activity indicator. Otherwise, they are open to trivial denial-of-service attacks by high-rate disco#info requests.
Services MUST NOT publish message activity indicators for MUCs which are not publicly listed (muc_public feature flag) or where users would need some kind of specific authorization to join (such as a password or the member affiliation).
No IANA interactions required.
The form field should be registered, eventually.
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The following requirements keywords as used in this document are to be interpreted as described in RFC 2119: "MUST", "SHALL", "REQUIRED"; "MUST NOT", "SHALL NOT"; "SHOULD", "RECOMMENDED"; "SHOULD NOT", "NOT RECOMMENDED"; "MAY", "OPTIONAL".
1. XEP-0045: Multi-User Chat <https://xmpp.org/extensions/xep-0045.html>.
2. XEP-0030: Service Discovery <https://xmpp.org/extensions/xep-0030.html>.
3. XEP-0308: Last Message Correction <https://xmpp.org/extensions/xep-0308.html>.
Note: Older versions of this specification might be available at https://xmpp.org/extensions/attic/
Promoted to Experimental
Initial submission.
@report{schäfer2024muc-activity,
title = {MUC Activity Indicator},
author = {Schäfer, Jonas},
type = {XEP},
number = {0502},
version = {0.1.0},
institution = {XMPP Standards Foundation},
url = {https://xmpp.org/extensions/xep-0502.html},
date = {2024-11-29/2024-12-23},
}END