THE COMMON ALERTING PROTOCOL:
AN OPEN STANDARD FOR INTEROPERABILITY IN ALL-HAZARD WARNING

The Common Alerting Protocol (CAP) is a simple, flexible data interchange format for collecting and distributing “all-hazard” safety notifications and emergency warnings over information networks and public alerting systems.

The Common Alerting Protocol (CAP) specifies an open, non-proprietary digital message format for all types of alerts and notifications. The CAP format is fully compatible with existing formats including the Specific Area Message Encoding (SAME) used for NOAA Weather Radio and the Emergency Alert System, while offering enhanced capabilities that include:

  • 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 Need

Warning systems in the United States today are “a patchwork of technologies and processes,” according to the national non-profit Partnership for Public Warning. Different systems have evolved to meet different threats in different places. Until now there’s been no way to distribute warnings consistently over all available channels. Nor has there been any way to monitor the whole picture of local, state and national warnings at any one time. Decisions about new alerting systems have been fraught with concerns about compatibility and operational complexity.

Background and Process

In November 2000 the National Science and Technology Council released a report on “Effective Disaster Warnings.” One key recommendation of the blue-ribbon panel was 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.”

During 2001 an international working group of more than 120 emergency managers and emergency information technologists developed initial requirements and a straw man design for CAP. In 2002 that effort was adopted by the Partnership for Public Warning (PPW), a national public-private partnership of agencies, vendors and academic experts. In 2003 PPW sponsored CAP into the OASIS standards process for refinement and testing. In April 2004, CAP 1.0 was adopted as an OASIS standard.

Compatibility, Flexibility and Benefits

CAP is a content standard, deliberately designed to be “transport-agnostic.” In web-services applications, CAP provides a lightweight standard for exchanging urgent notifications. CAP can also be used in data-broadcast applications and over legacy data networks.

CAP provides compatibility with all kinds of information and public alerting systems, including those designed for multilingual and special-needs populations. CAP is fully compatible with the existing national broadcast Emergency Alert System (EAS). A 2003 whitepaper describesPDF document details of the CAP/EAS interface.

CAP incorporates geospatial elements based on Open GIS Consortium recommendations to permit flexible but precise geographic targeting of alerts. It provides for associating digital images and other binary information with alerts. It supports various mechanisms for ensuring message authenticity, integrity and confidentiality (where required) including in particular the work of the OASIS Web Services Security and PKI Technical Committees.

The chief benefit of CAP will be reduction of costs and operational complexity by eliminating the need for multiple custom software interfaces to the many warning sources and dissemination systems involved in all-hazard warning. The CAP message format can be converted to and from the “native” formats of all kinds of sensor and alerting technologies, forming a basis for a technology-independent national and international “warning internet.”

Implementers and Supporters

A partial list of public and private organizations that have implemented CAP includes:

  • National Weather Service
  • United States Geological Survey
  • California Office of Emergency Services
  • Virginia Department of Transportation
  • Capital Wireless Integrated Network (CapWIN)
  • GeoDecisions, Inc.
  • E Team
  • Blue292
  • Warning Systems, Inc.
  • Comlabs, Inc.
  • mobileFoundations
  • Ship Analytics
  • MyStateUSA
  • IEM, Inc.
  • Hormann America, Inc.
  • Oregon RAINS
  • NDS, Ltd.

CAP-capable applications have been deployed in multi-vendor events and field trials in Washington, D.C., Virginia, Florida, Nevada and California. CAP data elements have been incorporated in the U.S. Department of Justice’s “Global Justice XML Data Model”.

CAP has been endorsed by the National Emergency Management Association’s Preparedness Committee, the Partnership for Public Warning, the ComCARE Alliance, the Emergency Interoperability Consortium and the Capital Wireless Integrated Network (CapWIN).

For More Information:

Contact Mr. Art Botterell, PPW Representative to OASIS and Chair of the CAP Working Group and the OASIS Emergency Management Notification Methods and Messages Subcommittee. He can be reached by email or (707) 425-4916.





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Last Updated: 04/21/2004