Common Alerting Protocol

The Common Alerting Protocol (CAP) is an XML-based data format for exchanging public warnings 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 Department of Homeland Security, the Department of the Interior's United States Geological Survey, and the Department of Commerce's National Oceanic and Atmospheric Administration (NOAA), and state and local government agencies 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 (SAME) used in Weatheradio and the broadcast Emergency Alert System as well as new technology such as the Commercial Mobile Alert System (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;
• Facility for digital images, audio, and video.