It is sometimes useful, while reading some conversations, to be reminded about it at some point in the future. This specification proposes a mechanism to allow clients to set up such reminders.
This protocol requires handling of dates and times, as such it conforms to XMPP Date and Time Profiles (XEP-0082) .
An entity may wish to discover if a service supports the Reminders feature; in order to do so, it sends a service discovery information query to the server..
If the server supports the Reminders feature, it MUST specify the 'urn:xmpp:reminders:0' feature in its service discovery information features as specified in Service Discovery (XEP-0030) 
For end users, this provides a way to be reminded about stuff while being in a conversation, without the need to leave it and go to some calendar application or similar and create a full event there. By setting a reminder, a user will be notified by the server at whatever given time the reminder is created with and with whatever the description was set for such a reminder.
A user wants to create a new reminder. For creating a reminder, an entity MUST send an IQ stanza with the 'type' attribute with a value of "set" and a direct <reminder/> child qualified by the "urn:xmpp:reminders:0" namespace.
Whenever the reminder's data sent by a client is not complete or in an invalid format, the server MUST send an error stanza of type 'modify' and a 'bad-request' condition.
In the event of a client trying to set a reminder in the past, the server MUST send an error stanza of type 'modify' and a 'gone' condition.
Whenever the time for a reminder arrives, the server MUST send a message with the reminder to the creating entity.
After sending a reminder, the server MAY choose to delete it from its storage.
There may be the case where a user wants to cancel an already set reminder. To do so, the client MUST send an IQ stanza of type 'set' with a 'reminder' child containing the 'id' attribute of the reminder to be deleted, without any additional child.
As stated in the requirements, the 'date' element MUST contain a valid XMPP Date and Time Profiles (XEP-0082)  DateTime value.
This document introduces no additional security considerations above and beyond those defined in the documents on which it depends.
No interaction with the Internet Assigned Numbers Authority (IANA)  is required as a result of this document.
This specification defines the following XML namespace:
Upon advancement of this specification from a status of Experimental to a status of Draft, the XMPP Registrar  shall add the foregoing namespace to the registry located at <https://xmpp.org/registrar/namespaces.html>, as described in Section 4 of XMPP Registrar Function (XEP-0053) .
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The Extensible Messaging and Presence Protocol (XMPP) is defined in the XMPP Core (RFC 6120) and XMPP IM (RFC 6121) specifications contributed by the XMPP Standards Foundation to the Internet Standards Process, which is managed by the Internet Engineering Task Force in accordance with RFC 2026. Any protocol defined in this document has been developed outside the Internet Standards Process and is to be understood as an extension to XMPP rather than as an evolution, development, or modification of XMPP itself.
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The following requirements keywords as used in this document are to be interpreted as described in RFC 2119: "MUST", "SHALL", "REQUIRED"; "MUST NOT", "SHALL NOT"; "SHOULD", "RECOMMENDED"; "SHOULD NOT", "NOT RECOMMENDED"; "MAY", "OPTIONAL".
3. The Internet Assigned Numbers Authority (IANA) is the central coordinator for the assignment of unique parameter values for Internet protocols, such as port numbers and URI schemes. For further information, see <http://www.iana.org/>.
4. The XMPP Registrar maintains a list of reserved protocol namespaces as well as registries of parameters used in the context of XMPP extension protocols approved by the XMPP Standards Foundation. For further information, see <https://xmpp.org/registrar/>.
Note: Older versions of this specification might be available at http://xmpp.org/extensions/attic/