<abstract>This document defines an XMPP protocol extension for retrieving information about the last activity associated with a Jabber entity.</abstract>
<remark><p>Per a vote of the XMPP Council, changed from Historical and Active to Standards Track and Draft; added Implementation Notes and clarified text throughout; added proviso to security considerations regarding client support; added section on Service Discovery.</p></remark>
<p>It is often helpful to know the time of the last activity associated with a entity. The canonical usage is to discover when a disconnected user last accessed the server. The 'jabber:iq:last' namespace provides a method for retrieving that information. The 'jabber:iq:last' namespace can also be used to discover when a connected user was last active on the server (i.e., the user's idle time) or to query servers and components about their current uptime.</p>
<p>In order to request last activity information regarding another entity, the requesting entity shall send an &IQ; stanza of type "get" to the target entity, containing a &QUERY; element qualified by the 'jabber:iq:last' namespace:</p>
<p>The target entity MUST return either an IQ-result or an IQ-error. When returning an IQ-result, the target entity sends an &IQ; stanza of type='result' containing a &QUERY; element with a REQUIRED 'seconds' attribute and OPTIONAL XML character data.</p>
<p>The requesting entity must interpret the IQ-result based on the responding entity's JID type in order to determine the meaning of the information. Specifically, the information means something different depending on whether the responding entity has a JID of the form 'host', 'user@host', or 'user@host/resource'. These differences are explained more fully below.</p>
<section1topic='Offline User Query'anchor='offline'>
<p>The primary usage of the 'jabber:iq:last' namespace is to find out how long ago a user logged out (and, additionally, what their status message was at that time). This primary usage assumes that the IQ-get is sent to a bare JID (&BAREJID;). When used in this way, the &QUERY; element contained in the IQ-result has a 'seconds' attribute, which is the number of seconds that have passed since the user last logged out. In addition, the element MAY contain XML character data that specifies the status message of the last unavailable presence received from the user. An example is shown below:</p>
<p>In this example, the user logged out fifteen minutes and three seconds ago, and when they logged out they sent a presence packet of type='unavailable' whose <status/> element contained the text "Heading Home".</p>
<p>If the user has at least one available resource when the server receives the request, the response SHOULD contain an empty <query/> element whose 'seconds' attribute is set to a value of '0'.</p>
<p>Note well that, as specified in &xmppcore; and &xmppim;, an IQ query sent to a JID of the form user@host is handled by a server on the user's behalf, not forwarded to one or more active resources. In addition, a server MUST NOT return last activity information to an entity that is not authorized to view the user's presence information (normally via presence subscription), and MUST return a "Forbidden" error in response to such a request (for information about error conditions, refer to &xep0086;).</p>
<p>Support for this functionality is OPTIONAL (a client that does not support the protocol, or that does not wish to divulge this information, SHOULD return a &unavailable; error).</p>
<p>If there is no available resource matching the user@host/resource in the 'to' attribute of the request, the server MUST follow the rules in <strong>XMPP IM</strong> in order to determine what error stanza to return.</p>
<section1topic='Server and Component Query'anchor='server'>
<p>When the IQ-get namespace is sent to a server or component (i.e., to a JID of the form 'host'), the information contained in the IQ reply reflects the uptime of the JID sending the reply. The seconds attribute is how long the host has been up. The &QUERY; element SHOULD NOT contain XML character data.</p>
<p>In order for a requesting entity to determine if a responding entity supports result set management, it SHOULD send a &xep0030; information request to the responding entity:</p>
<p>The information contained in an IQ reply for this namespace is inherently ambiguous. Specifically, for a bare JID (&BAREJID;) the information is the time since the JID was last connected to its server; for a full JID (&FULLJID;) the information is the time since the resource was last active in the context of an existing session; and for a bare domain the information is the uptime for the server or component. An application must take these differences into account when presenting the information to a human user.</p>
<p>A server MUST NOT allow an unauthorized entity to learn a user's network availability by sending a Last Activity request to a JID of the form user@host or user@host/resource; i.e., Last Activity information MAY be divulged only to those entities that have permission to view the user's presence via a presence subscription (potentially as restricted by &xep0016; or &xep0191;).</p>
<p>A client MUST provide a way for a human user to disable sending of Last Activity responses from the client's full JID (&FULLJID;).</p>
<p>No action on the part of the ®ISTRAR; is necessary as a result of this document, since 'jabber:iq:last' is already a registered protocol namespace.</p>
