The Common Alerting Protocol  (CAP) is an open format for alerts and notifications, defined by OASIS . CAP was developed to address the call, published in a (U.S.) National Science and Technology Council report, for "a standard method ... to collect and relay instantaneously and automatically all types of hazard warnings and reports". Given that the Extensible Messaging and Presence Protocol (see XMPP Core ) provides a near-real-time transport mechanism for structured information, and that CAP is defined as an XML data format, it makes sense to define a way to transport CAP information over XMPP. Such a method is defined herein.
The keywords "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119 .
Because the alerts and notifications structured via CAP require a "push" medium, they SHOULD be sent via the XML <message/> stanza defined in XMPP Core. The message could be sent using either of the following methods:
Both methods are described below.
In the case of direct messages, the message stanza SHOULD have no 'type' attribute, but MAY have any defined type that is appropriate to the communications context (e.g., "groupchat" in a text conference). The <alert/> element SHOULD be the only child element of the message stanza, but other elements MAY be included as necessary (e.g., a <body/> child in the 'jabber:client' namespace providing a natural-language description of the alert). The 'id' attribute of the <message/> stanza MAY be set to the value of the CAP <identifier/> element.
The following example shows Example A.2 from the CAP specification sent as a direct message.
The publish-subscribe protocol defined in XEP-0060 provides a way to send information to a number of subscribers, and to control the list of subscribers.
The following example shows Example A.2 from the CAP specification published to a pubsub node.
If the pubsub node is configured to deliver payloads, the information is then sent to all subscribers.
Security considerations for CAP are defined in Common Alerting Protocol, v. 1.0; security considerations for XMPP are defined in RFC 3920: XMPP Core; security considerations for the XMPP publish-subscribe extension are defined in XEP-0060: Publish Subscribe.
Furthermore, it may be appropriate to include the "Classification", "Distribute", and/or "Store" headers specified in Stanza Headers and Internet Metadata (XEP-0131)  in order to safeguard CAP data.
This document requires no interaction with the Internet Assigned Numbers Authority (IANA) .
No namespaces or parameters need to be registered with the XMPP Registrar  as a result of this document.
The CAP information format is defined by an XML schema. The reader is referred to the CAP specification for the relevant schema definition.
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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.
The primary venue for discussion of XMPP Extension Protocols is the <email@example.com> discussion list.
Discussion on other xmpp.org discussion lists might also be appropriate; see <http://xmpp.org/about/discuss.shtml> for a complete list.
Errata can be sent to <firstname.lastname@example.org>.
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".
1. Common Alerting Protocol, v. 1.0 <http://www.oasis-open.org/committees/documents.php?wg_abbrev=emergency>.
9. 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/>.
10. 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/