Roster item exchanges can be sent in any of the four following ways:
In an &IQ; stanza to a full JID &LOCALFULL;. This is appropriate if the sender has knowledge (e.g., via presence and &xep0115;) that a particular resource associated with the recipient is online and supports this protocol.
In an &IQ; stanza to a bare JID &LOCALFULL;. This can be appropriate if the sender wants the roster item to be processed by the server on behalf of the recipient (e.g., if the sender is a trusted component of the server).
In an &IQ; stanza to a bare JID &LOCALBARE;. This can be appropriate if the sender wants the roster item to be processed by the server on behalf of the recipient (e.g., if the sender is a trusted component of the server).
In a &MESSAGE; stanza to a bare JID &LOCALBARE;. This can be appropriate if the sender wants the roster item to be delivered to all of the recipient's online resources (e.g., because the sender does to have presence or capabilities information about particular resources).
In a &MESSAGE; stanza to a full JID &LOCALFULL;. This is generally undesirable, since it is better to se an &IQ; stanza when sending to a full JID (e.g., IQ stanzas are automatically acknowledged).