Even though a client might be available (as stated in the most recent presence stanza), the user this client belongs to might not be focused on the client currently. &xep0132; defines a method for a physical test of user presence. Since this requires special hardware that can not be assumed to be available, this XEP defines a software-only implementation where no direct feedback is expected. This is known as 'nudge' or 'buzz' in some legacy IM protocols.

It was discussed whether this should be part of &xep0085;. However, the semantics are inherently different, since it describes the sender's state, not a request to change the receiver's. Thus, a separate extension is desirable.

The specification addresses remotely getting the user's attention in a more assertive way than simple text messages.

In the following conversation, a user talks to somebody, but this user doesn't respond. The second inquiry includes an attention extension.

When no reply is received, the sending user might want to grab the other's attention. This is done by sending a message that includes an <attention/> element qualified by the 'urn:xmpp:attention:0' namespace &VNOTE;. Note: The message may or may not include a &BODY; element.

Finally, the receiving user notices the urgency of the message and responds.

The following rules apply to generating and processing of the attention extension.

1. Before sending an attention message stanza, the client SHOULD confirm support for it in the other client as described under Determining Support.
2. The message stanza containing the attention extension MAY contain a body and/or other extensions, which is to be displayed along with executing the attention event.
3. In message stanzas containing either &xep0203; data, attention extensions MUST be ignored, since this is an instant event which should not be replayed after a delay.
4. Messages containing an attention extension SHOULD use the headline message type to avoid offline storage.
5. Using the attention extension in &IQ; stanzas is not desirable, since this is part of the conversation.

If an entity supports receiving the attention extension, it MUST advertise that fact in its responses to &xep0030; information ("disco#info") requests by returning a feature of "urn:xmpp:attention:0":

In order for an application to determine whether an entity supports this protocol, where possible it SHOULD use the dynamic, presence-based profile of service discovery defined in &xep0115;. However, if an application has not received entity capabilities information from an entity, it SHOULD use explicit service discovery instead.

The implementation of the alert is up to the developer. Possible behavior is:

• Shaking the window.
• Playing a specific sound not used for any other event.
• Flashing the screen.
• Enabling external hardware such as flashlights.
• Let it be user customizable.

However, since some users might not want this feature to disturb them, a client SHOULD allow the user to disable support. When the feature is disabled, it MUST NOT be advertised in disco#info.

Rate-limiting might be desirable in some implementations.

Formal feedback in response to the attention request to the requesting user is not specified, and so the request might be silently dropped.

It is RECOMMENDED that only message stanzas containing attention extensions from peers on the user's roster are accepted. Finer grained control might be implemented.

This document requires no interaction with &IANA;.

The quotes have been taken from Isaac Asimov's short story "Liar!" as published in the book The Complete Robot.