The document discusses the importance of location information in emergency management systems, specifically focusing on the interoperability between the Common Alerting Protocol (CAP) and Presence Information Data Format - Location Object (PIDF-LO) for effective early warning dissemination. It highlights the role of the IETF in defining frameworks for internet geolocation and emphasizes the need for CAP messages to reach relevant recipients based on their geodetic or civic locations. The document concludes that addressing interoperability issues between CAP and PIDF-LO is essential for enhancing emergency response capabilities.

1. Institut für
Computertechnik
ICT
Institute of
Computer Technology
Location Information
Interoperability of
CAP and PIDF-LO for
Early Warning Systems
Karl Wolf

2. Institut für Computertechnik 2
Overview
 Location information is the key information for emergency
management
 Common Alerting Protocol (CAP) is implemented by several Early
Warning Systems
 CAP messages describe the affected area
 CAP alert messages can be delivered directly to alert recipients over
various networks
 Location-aware receivers can determine, whether the alert is relevant
for the current location
 Internet devices are becoming increasingly location-aware
 Framework for a unified location system for the Internet was defined by
the Internet Engineering Task Force (IETF)
 Internet location services allow devices to acquire their current location
as Presence Information Data Format – Location Object (PIDF-LO)
 Location format interoperability of CAP and PIDF-LO is required

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Architecture
Architecture implemented as prototype

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Presence Information Data Format –
Location Object (PIDF-LO)
 XML document defined by the IETF
 Geodetic and civic location supported
 Civic address: predefined types (country, A1-A6, street,
house number, …)
 Geodetic location: various shapes (point, polygon, circle,
ellipse, arc band, …)
 Central role in the IETF’s framework for Internet
geolocation (e.g. location configuration protocols)
 Adopted for next generation emergency calling in
North America by the National Emergency Number
Association (NENA)

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The Common Alerting Protocol (CAP)
 CAP 1.2 adopted by Organization for the
Advancement of Structured Information
Standards (OASIS) in 2010
 XML data format for all kinds of alerts
 Affected area
 Textual description
 Geodetic shapes: circle and polygon
 Geocode: name value pair (no predefined names)

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Geodetic Interoperability
 CAP and PIDF-LO are supporting geodetic
location information
 Well known algorithms can be used
 Example: point-in-polygon query to determine,
whether a point in PIDF-LO lies within our
outside boundaries of a CAP polygon

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Civic Location Interoperability
 PIDF-LO is supporting civic addresses
(predefined elements: country, street, etc.)
 CAP specification does not mention civic
addresses
 CAP has geocode elements (no predefined
elements)
 Structure of civic addresses is more complex
 How to figure out, whether a civic address lies
inside an area?
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Civic Location Interoperability - Example
<area>
<areaDesc>
Santa Clarita Valley
</areaDesc>
<geocode>
<valueName>UGC</valueName>
<value>CAZ088</value>
</geocode>
</area>
<cl:civicAddress xml:lang="en">
<cl:country>US</cl:country>
<cl:A1>California</cl:A1>
<cl:A2>Los Angeles County</cl:A2>
<cl:A3>Santa Clarita</cl:A3>
<cl:RD>Railroad</cl:RD>
<cl:STS>Ave</cl:STS>
<cl:HNO>24875</cl:HNO>
<cl:PC>CA 91321</cl:PC>
</cl:civicAddress>
Exemplary CAP area representation (left) and PIDF-LO civic address (right)

9. Institut für Computertechnik
Options
 Forbid usage of civic addresses in PIDF-LO?
 PIDF-LO is typically generated by a different entity than CAP
 Civic addresses are also supported in the next generation
emergency calling framework
 Civic addresses are suitable for certain scenarios (e.g. location
server serving fixed subscriber line customers)
 Convert civic address to geodetic location?
 Geocoding service necessary
 Error-prone
 Include PIDF-LO civic address elements in CAP?
 New civic address element or full PIDF-LO inside CAP
 Usage of geocode element (used for prototype implementation)
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10. Institut für Computertechnik
Example
<area>
<areaDesc>Santa Clarita</areaDesc>
<geocode>
<valueName>PIDF-LO</valueName>
<value>
country="US";A1="California";
A2="Los Angeles County";A3="Santa Clarita“
</value>
</geocode>
</area>
Area representation in CAP with geocode element containing PIDF-LO
civic address elements for interoperability.
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Conclusion
 IETF Internet geolocation makes devices location-aware
and allows location-based services to benefit
 PIDF-LO was adopted for next generation emergency calling in
North America
 Early warning could also benefit when CAP is disseminated to
end devices – only affected people get notified
 Dissemination of warnings in geodetic as well as in civic
location format is required
 CAP generators have no knowledge about the format the
receivers have configured
 Interoperability issue for civic addresses exists
 PIDF-LO civic address types would be required in CAP
 Further work is required to prevent different
implementations on the Internet