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Subject: CAP Use Scenarios Draft

Friends -

As I went back to the books on writing use cases, I realized that 
design use cases are very useful for describing processes, but not 
quite so handy for describing events, which is really what individual 
messages are.

So what I'm offering here for your discussion aren't so much use 
cases (except perhaps in the dreaded "business use case" sense!) as 
they are just illustrations of some potential real-world applications.

- Art

Use Scenarios - Common Alerting Protocol Message Format
draft 5/11/2003

The following scenarios illustrate a few possible use cases for the 
Common Alerting Protocol message format.  [Note that at this point we 
are discussing only the message itself, not the telecommunications or 
applications architecture(s) that support(s) it.]

I - Manual Origination

The Incident Commander at an industrial fire with potential of a 
major explosion decides to issue a public alert with three 
components:  a) An evacuation of the area within half a mile of the 
fire; b) a shelter-in-place instruction for people in a polygon 
roughly describing a downwind dispersion "plume" extending several 
miles downwind and half a mile upwind; and c) a request for all media 
and civilian aircraft to remain above 2500 feet above ground level 
when within half a mile of the incident.

Using a portable computer and a web page (and a pop-up drawing tool 
to enter the polygon) the Incident Commander issues the alert as a 
CAP message to a local alerting network.

II - Automated Origination by Sensor System

Along a popular Northwest beach a series of automatic tsunami sirens 
have been installed.  In the base of each siren is an accelerometer 
and a computer with a GPS receiver.  All of these devices are linked 
by a wireless local area network.

When an individual unit detects what appears to be a P-wave/S-wave 
sequence that might indicate a near-shore earthquake, it generates a 
CAP message containing its location, the precise time of the P-wave's 
arrival, and the estimated distance of the epicenter based on the 
P-wave/S-wave interval.

Each computer in the network correlates all the messages received 
from the other instruments (which form what amounts to a phased 
array) and, if the pattern of messages suggests a near-shore quake 
(and not just a truck driving down the coastal highway) then each 
siren activates.  In addition, one of the instruments assembles a 
"summary" CAP message describing the event and feeds it to regional 
and national seismic networks.

(Based on an idea shared by David Oppenheimer at the USGS in Menlo Park.)

III - Aggregation and Correlation on Real-time Map

At the State Operations Center a computerized map of the state 
depicts, in real time, all current and recent warning activity 
throughout the state.  All major warning systems in the state... the 
Emergency Alert System, siren systems, telephone alerting and other 
systems... have been equipped to report the details of their 
activation in the form of a CAP message.  (Since many of them are now 
activated by way of CAP messages, this is frequently just a matter of 
forwarding the activation message to the state center.)

Using this visualization tool, state officials can monitor for 
emerging patterns of local warning activity and correlate it with 
other real time data (e.g., telephone central office traffic loads, 
9-1-1 traffic volume, seismic data, automatic vehicular crash 
notifications, etc.)

IV - Integrated Public Alerting

As part of an integrated warning system funded by local industry, all 
warning systems in a community can be activated simultaneously by the 
issuance by authorized authority of a single CAP message.

Each system converts the CAP message data into the form suitable for 
its technology (text captioning on TV, synthesized voice on radio and 
telephone, activation of the appropriate signal on sirens, etc.) 
Systems that can target their messages to particular geographic areas 
implement the targeting specified in the CAP message with as little 
"spill" as their technology permits.

In this way, not only is the reliability and reach of the overall 
warning system maximized, but citizens also get corroboration of the 
alert through multiple channels, which increases the chance of the 
warning being acted upon.

V - Repudiating A False Alarm

Inadvertently (or perhaps not, but that will be the subject of 
investigation later on) the integrated alerting network has been 
activated with an inaccurate warning message.

This activation comes to officials' attention immediately through 
their own monitoring facilities (e.g., III above).  Having determined 
that the alert is, in fact, inappropriate, the officials issue a 
cancellation message that refers directly to the erroneous prior 
alert.  Alerting systems that are still in the process of delivering 
the alert (e.g., telephone dialing systems) stop doing so.  Broadcast 
systems deliver the cancellation message. Other systems (e.g., 
highway signs) simply reset to their normal state.


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