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Common Alerting Protocol

Common Alerting Protocol

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The Common Alerting Protocol (CAP) is an XML
Extensible Markup Language is a set of rules for encoding documents in machine-readable form. It is defined in the XML 1.0 Specification produced by the W3C, and several other related specifications, all gratis open standards....

-based data format for exchanging public warnings
Emergency population warning
An emergency population warning is a method whereby local, regional, or national authorities can contact members of the public en masse to warn them of an impending emergency...

 and emergencies between alerting technologies. CAP allows a warning message to be consistently disseminated simultaneously over many warning systems to many applications. CAP increases warning effectiveness and simplifies the task of activating a warning for responsible officials.

Individuals can receive standardized alerts from many sources and configure their applications to process and respond to the alerts as desired. Alerts from the United States Geological Survey
United States Geological Survey
The United States Geological Survey is a scientific agency of the United States government. The scientists of the USGS study the landscape of the United States, its natural resources, and the natural hazards that threaten it. The organization has four major science disciplines, concerning biology,...

, the Department of Homeland Security, NOAA and the California Office of Emergency Services can all be received in the same format, by the same application. That application can, for example, sound different alarms based on the information received.

By normalizing alert data across threats, jurisdictions and warning systems, CAP also can be used to detect trends and patterns in warning activity, such as trends that might indicate an undetected hazard or hostile act. From a procedural perspective, CAP reinforces a research-based template for effective warning message content and structure.

The CAP data structure is backward-compatible with existing alert formats including the Specific Area Message Encoding
Specific Area Message Encoding
Specific Area Message Encoding or SAME is the protocol used to encode the Emergency Alert System and NOAA Weather Radio's SAME Public Warning System in the U.S...

 (SAME) used in Weatheradio and the broadcast Emergency Alert System
Emergency Alert System
The Emergency Alert System is a national warning system in the United States put into place on January 1, 1997, when it superseded the Emergency Broadcast System , which itself had superseded the CONELRAD System...

 as well as new technology such as the Commercial Mobile Alert System
Commercial Mobile Alert System
The Commercial Mobile Alert System , also known as the Personal Localized Alerting Network , is an alerting network designed to disseminate emergency alerts to mobile devices such as cell phones and pagers...

 (CMAS), while adding capabilities including:
  • Flexible geographic targeting using latitude/longitude “boxes” and other geospatial representations in three dimensions;
  • Multilingual and multi-audience messaging;
  • Phased and delayed effective times and expirations;
  • Enhanced message update and cancellation features;
  • Template support for framing complete and effective warning messages;
  • Digital encryption and signature capability; and,
  • Facility for digital images, audio and video.


The National Science and Technology Council
National Science and Technology Council
The National Science and Technology Council was established in the US by Executive Order 12881 on November 23, 1993.-History:The National Science and Technology Council was established in the US by Executive Order on November 23, 1993...

 (NSTC) report on “Effective Disaster Warnings” PDF (November, 2000) recommended that “a standard method should be developed to collect and relay instantaneously and automatically all types of hazard warnings and reports locally, regionally and nationally for input into a wide variety of dissemination systems.”

In 2001 an international, independent group of over 120 emergency managers began specifying and prototyping the Common Alerting Protocol data structure based on the recommendations of the NSTC report. The project was embraced by the non-profit Partnership for Public Warning and a number of international warning system vendors. A series of field trials and long-term demonstration projects during 2002-03 led to the submission of a draft CAP specification to the OASIS standards process for formalization.

The CAP 1.0 specification was approved by OASIS
OASIS (organization)
The Organization for the Advancement of Structured Information Standards is a global consortium that drives the development, convergence and adoption of e-business and web service standards...

 in April, 2004. Based on experience with CAP 1.0, the OASIS Emergency Management Technical Committee adopted an updated CAP 1.1 specification in October 2005. At a meeting in Geneva in October, 2006 the CAP 1.1 specification was taken under consideration by the International Telecommunications Union for adoption as an ITU recommendation.

Current Implementations

According to a CAP 1.0 Fact Sheet, CAP implementations have been demonstrated by agencies and companies including: United States Department of Homeland Security
United States Department of Homeland Security
The United States Department of Homeland Security is a cabinet department of the United States federal government, created in response to the September 11 attacks, and with the primary responsibilities of protecting the territory of the United States and protectorates from and responding to...

; National Weather Service
National Weather Service
The National Weather Service , once known as the Weather Bureau, is one of the six scientific agencies that make up the National Oceanic and Atmospheric Administration of the United States government...

; United States Geological Survey
United States Geological Survey
The United States Geological Survey is a scientific agency of the United States government. The scientists of the USGS study the landscape of the United States, its natural resources, and the natural hazards that threaten it. The organization has four major science disciplines, concerning biology,...

; California Office of Emergency Services; Virginia Department of Transportation; GeoDecisions, Inc.; Blue292; Warning Systems, Inc.; Comlabs, Inc.; mobileFoundations; Ship Analytics; MyStateUSA; IEM, Inc.; Hormann America, Inc.; Oregon RAINS; Alerting Solutions, Inc. and others.

It is also mentioned by the Internet Society
Internet Society
The Internet Society or ISOC is an international, nonprofit organization founded during 1992 to provide direction in Internet related standards, education, and policy...

 in its 2005 "Public Warning Network Challenge".

During early 2005 the U.S. Department of Homeland Security (DHS), in partnership with the Association of Public Television Stations, demonstrated CAP-based "digital EAS" broadcasts over public television digital TV transmitters and satellite links in the Washington, D.C. area and nationwide.

CAP is the foundation technology for the planned "Integrated Public Alert and Warning System," an all-hazard, all-media national warning architecture being developed by DHS, the National Weather Service and the Federal Communications Commission.

In Canada, a working group composed of public alerting practitioners and government agencies has developed a CAP Canadian Profile (CAP-CP) based on CAP but specialized to address the needs of Canadian public alerting stakeholders, such as bilingualism, geocoding for Canada, managed lists of locations and events, etc. The Canadian government has adopted CAP-CP for its National Public Alerting System (NPAS) project. The CAP-CP working group, along with stakeholders and projects such as the Canadian Association for Public Alerting and Notification (CAPAN) and Netalerts' Sarnia Lambton trial, are now working with and refining CAP-CP for national application in Canada.

CAP has been implemented for a small-scale, grassroots hazard information system in Sri Lanka
Sri Lanka
Sri Lanka, officially the Democratic Socialist Republic of Sri Lanka is a country off the southern coast of the Indian subcontinent. Known until 1972 as Ceylon , Sri Lanka is an island surrounded by the Indian Ocean, the Gulf of Mannar and the Palk Strait, and lies in the vicinity of India and the...

 following the 2004 Indian Ocean Tsunami. This implementation was part of the "HazInfo Project" funded by Canada's International Development Research Centre.

In 2007, the International Telecommunication Union, Telecommunication Standardization Sector (ITU-T) adopted the Common Alerting Protocol as Recommendation X.1303. The recommendation annex contains an authoritative ASN.1 module translation of the CAP XML schema that may be useful for some implementations. Rec. X.1303 is within the remit of ITU-T Study Group 17 (Security), Rapporteur Group on Cybersecurity (Q.4/17) http://www.itu.int/ITU-T/studygroups/com17/index.asp for purposes of further evolution of the standard.

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