World Meteorological Organization (WMO)
Observing and Information Systems Department
Common Alerting
Protocol (CAP)
Presented 26 September 2008 at
Joint Implementation-coordination Meeting on the GTS-WIS MTN
and Meeting of the CBS Expert Team on
GTS-WIS Operations and Implementation (ET-OI)
by Eliot Christian <>
Today's Public Warning Patchwork
Every government has various public warning systems:
 Weather by news wire, by radio, by television,
by e-mail, by SMS text on cell phones ...
 Earthquakes by e-mail, by news wire, by Web
sites, by pagers, by telephone calls ...
 Amber alerts by highway signs, by fax,
by phone trees, by Web sites, by police radio...
 Civil defense by television, by radio, by sirens,
by police with bullhorns...
 And on, and on ...
4 October 2015
Common Alerting Protocol (CAP)
The New Strategy for Public Warning
 Governments now realize it makes no sense
to build separate public warning systems
for each particular type of emergency and
for each particular communications medium
 Instead, efficiency and effectiveness argue
for addressing public warning requirements
with all-media coverage across all-hazards
through the use of common standards
4 October 2015
Common Alerting Protocol (CAP)
A Case in Point:
The Common Alerting Protocol (CAP) Standard
CAP is a standard message format especially designed
for All-Media, All-Hazard, communications:
 over any and all media (television, radio, telephone,
fax, highway signs, e-mail, Web sites, RSS "Blogs", ...)
 about any kind of hazard situation (Weather, Fires,
Earthquakes, Volcanoes, Landslides, Child Abductions,
Disease Outbreaks, Air Quality Warnings, Beach
Closings, Transportation Problems, Power Outages, ...)
 to anyone: the public at large; designated groups
(civic authority, responders, etc.); or specific people
4 October 2015
Common Alerting Protocol (CAP)
Google Earth example using open standards
Structure of a CAP Alert
CAP Alert messages
 Text values for human
readers, e.g., "headline",
"area description", etc.
 Coded values useful for
filtering, routing, and
automated translation
to human languages
4 October 2015
Common Alerting Protocol (CAP)
Internal Structure of a CAP Alert (e.g., XML)
The Content Standard for Alerts: CAP
Filtering and Routing Criteria
 Date/Time
 Geographic Area
(polygon, circle, geographic codes)
 Status
(Actual, Exercise, System, Test)
 Scope
(Public, Restricted, Private)
 Type
(Alert, Update, Cancel, Ack, Error)
4 October 2015
Common Alerting Protocol (CAP)
The Content Standard for Alerts: CAP
Filtering and Routing Criteria
 Event Categories
(Geo, Met, Safety, Security, Rescue,
Fire, Health, Env, Transport, Infra, Other)
 Urgency: Timeframe for responsive action
(Immediate, Expected, Future, Past, Unknown)
 Severity: Level of threat to life or property
(Extreme, Severe, Moderate, Minor, Unknown)
 Certainty: Probability of occurrence
(Very Likely, Likely, Possible, Unlikely, Unknown)
4 October 2015
Common Alerting Protocol (CAP)
Typical CAP-based Alerting Systems
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Common Alerting Protocol (CAP)
Displaying CAP Alerts
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Common Alerting Protocol (CAP)
RSS and CAP Feeds from USGS
RSS for USGS Earthquake Data
Global Disaster Alert and Coordination System (GDACS)
4 October 2015
Common Alerting Protocol (CAP)
The CAP Standard (X.1303)
 Compatible with legacy as well as newer
transports (WMO messages, news wires,
digital TV, Web Services, ...)
 Flexible geographic targeting
 Phased and delayed effective time, expiration
 Message update and cancellation features
 May include inline digital images and audio
 Approved by OASIS as Version 1.1 (2005)
 Adopted as ITU Recommendation X.1303 (2006)
 Significant uptake, many implementations
4 October 2015
Common Alerting Protocol (CAP)
ITU Resolution 136 (Antalya, 2006)
"The Plenipotentiary Conference [...] resolves
to instruct the Directors of the Bureaux [...]
to promote implementation by appropriate
alerting authorities of the international content
standard for all-media public warning,
in concert with ongoing development of
guidelines by all ITU Sectors for application
to all disaster and emergency situations"
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Common Alerting Protocol (CAP)
NEWS -- Federal Communications Commission --May 31, 2007
"Washington, D.C. - The Federal Communications Commission
today adopted [an Order that] requires [Emergency Alert
System (EAS)] participants to accept messages using
Common Alerting Protocol (CAP) [...]
The use of CAP will help to ensure the efficient and
rapid transmission of EAS alerts [...] in a variety of formats
(including text, audio and video) and via different means
(broadcast, cable, satellite, and other networks) [...]
In addition, the Order expands the EAS system by
requiring participation by wireline video providers."
4 October 2015
Common Alerting Protocol (CAP)
CAP Implementers Workshop
OASIS Emergency Management TC
ITU-OASIS Workshop on Public Warning (2006)
Contact Eliot Christian <>
4 October 2015
Common Alerting Protocol (CAP)

Pilot Implementations of CAP in DOI