Which XEPs or eJabberd modules would be most suitable for conditionally and immediately changing the group of users a user is subscribed to?

Question

Imagine that a database connected to an XMPP server stores users, it also stores an extra data column (let's call it dataId) for each user. The data column can take on three values: 1, 2, or 3.

In an XMPP client that logs in to the server, a list of users is displayed along with their XMPP presence status. The list displays users that all have the same value of of dataId. The client can change the dataId value that is displayed, meaning that if he switches the value, then the user is now somehow subscribed to the presence of the new list of users, but not to the old list of users.

I wonder if someone with experience with XMPP has a suggestion as to which XEPs or corresponding eJabberd (or Prosody) modules could be used or are best suited for this type of functionality.

I am slowly going through the XEPs, but there are a lot of them, and it's not clear as of yet which modules could be used, or if I would perhaps need to set up some custom code on my XMPP server to handle this.

Answer 1

You can take a look at XEP-0140. This behaves similar to rosters except that all users in a shared roster group will be able to see all other users in the group. You can create multiple shared roster groups and easily switch a user between them by adding or removing the user from the group. You can also have nested groups. You can look at the example on using shared roster groups for different cases here, using ejabberd.