The existence of two different invitation methods might cause confusion among client developers.
(The room MUST NOT send any discussion history before it finishes sending room presence as specified in the Presence Broadcast section of this document.) Whether such history is sent, and how many messages comprise the history, shall be determined by the chat service implementation or specific deployment depending on local service policy or room configuration. Delivery of Discussion History  information qualified by the 'urn:xmpp:delay' namespace to indicate that they are sent with delayed delivery and to specify the times at which they were originally sent.
Service Sends New Occupant's Presence to New Occupant After sending initial presence as shown above, depending on local service policy or room configuration a room MAY send discussion history to the new occupant.
itself (a service MAY ignore or reject messages that do not have a type of "groupchat").
The following examples illustrate the use of this feature. User Requests Limit on Number of Characters in History Obviously the service SHOULD NOT return all messages sent in the room since the beginning of the Unix era, and SHOULD appropriately limit the amount of history sent to the user based on service or room defaults. User Requests No History After the room has sent the room subject, it SHALL begin to send live messages, presence changes, occupant "joins" and "leaves", and other real-time traffic to the new occupant, as described in other sections of this document.
This is done by including a status code of "170" in the initial presence that the room sends to the new occupant: Example 34.
If the user is entering a room in which the discussions are logged to a public archive (often accessible via HTTP), the service SHOULD allow the user to enter the room but MUST also warn the user that the discussions are logged.
Direct invitations were the original method used in the early Jabber community's "groupchat 1.0" protocol.
Service Passes Along Changed Presence to All Occupants There are two ways of inviting another user to a room: direct invitations and mediated invitations.
The invitee MAY choose to formally decline (as opposed to ignore) the invitation; and this is something that the sender might want to be informed about.