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Subject: CAP over Atom (Please review)
At PubSub.com, we’ve started
generating “CAP over Atom” files. By this I mean CAP messages which
are encapsulated in Atom Feed Files as defined in: http://www.mnot.net/drafts/draft-nottingham-atom-format-02.html
. We’ve started with CAP encodings of the Earthquake data that we’ve
been working with recently. The Atom format, which is currently
being updated and redefined in the Atom-Pub IETF Working Group, is widely
understood and processed by “RSS news aggregator” software. We’re
using this format as a “packaging” format for streams of CAP messages
since no other widely implemented formats really seem appropriate for the task
and since CAP itself defines no such “stream” format. In any case,
providing CAP data wrapped in the Atom format means that the millions of people
who have news aggregators will be able to view CAP messages with no requirement
to update or obtain new software. (Although better display and information will
be provided by news aggregators that actually understand the CAP format…) In order to provide the minimum
elements required by Atom and to ensure that news aggregators have useful
information to display even if they don’t understand the CAP format, we
are forced to copy a number of the CAP elements into Atom elements. I believe
any application of “CAP over Atom” will be required to do much the
same. The duplication of data is unfortunate, but necessary. If “CAP over
Atom” is accepted as something which is useful, it might be a good idea to
generate a set of general guidelines for packaging CAP in Atom feeds. What we’ve done is: 1. Copied alert:info:headline
to atom:title. 2. Copied alert:info:description
to atom:summary 3. Copied alert:info:web
to atom:link 4. Generated an
atom:id based on the CAP incident id using the tagUri scheme. See: http://www.taguri.org/ For a sample Atom feed containing
CAP messages which describe recent earthquakes, please see: http://atom.pubsub.com/c0/b8/bd62e8e48058c0425193b37ea6.xml Note: If you view the Atom feed above
in a web browser, the result may not be terribly pleasing… We’re
still working on the style sheet. – Please pay attention only to the
source of the feed… (i.e. do “View Source”). I would appreciate any comments you
might have on our use of Atom as a packaging mechanism for streams of CAP messages. A
sample atom:entry from the Atom Feed above appears below: <entry> <ps:nodeID>/pubsub/topics/301</ps:nodeID> <title><![CDATA[ Earthquake: M 1.6 (D) NORTHERN
CALIFORNIA 2005-02-04T02:00:43.100Z ]]></title> <issued>2005-02-03T21:04:42-05:00</issued> <modified>2005-02-03T21:04:42-05:00</modified> <id>tag:pubsub.com,2005:CAP:nc51156375</id> <link rel='alternate' type='text/html'
href='http://earthquake.usgs.gov/recenteqsUS/Quakes/nc51156375.htm'/> <summary>An earthquake occurred at
2005-02-04T02:00:43.100Z. The magnitude 1.6 event has been located in <content type='text/xml'> <alert
xmlns="http://www.incident.com/cap/1.0"> <identifier>nc51156375</identifier>
<sender>earthquakes@pubsub.com</sender>
<sent>2005-02-03T21:04:42-05:00</sent>
<status>Test</status>
<msgType>Alert</msgType>
<scope>Public</scope>
<incidents>nc51156375</incidents> <info>
<category>Geo</category>
<event>Earthquake</event>
<urgency>Unknown</urgency>
<severity>Unknown</severity>
<certainty>Unknown</certainty>
<senderName>Pubsub Earthquake Service</senderName> <headline>Earthquake:
M 1.6 (D) NORTHERN CALIFORNIA 2005-02-04T02:00:43.100Z</headline>
<description>An earthquake occurred at 2005-02-04T02:00:43.100Z. The
magnitude 1.6 event has been located in
<web>http://earthquake.usgs.gov/recenteqsUS/Quakes/nc51156375.htm</web>
<parameter>EventID=nc51156375</parameter>
<parameter>Version=1</parameter>
<parameter>Magnitude=1.6 MD</parameter>
<parameter>Depth=2 km</parameter>
<parameter>Verified=N</parameter> <area>
<areaDesc>2 km depth at latitude 38.8168, longitude -122.7915 at
location:
<circle>38.8168,-122.7915 0</circle> </area> </info> </alert> </content> </entry> Note: 1. We’ve
set the status of all messages to “Test”… 2. We’re
uncertain how to determine the values for urgency, severity, and certainty. Thus,
we’ve set them all to “Unknown.” 3. We are using
the same value for identifier and incident. This appears to be reasonable…
Is it? This service compliments the Earthquake
service that I recently mentioned on this list. We will be publishing both raw
Earthquake messages/feeds as well as CAP messages/feed in the future. These two
formats are targeted at different audiences. Once
we’ve done a bit more testing, we’ll announce how to access the user
interface to create custom subscriptions to these feeds. Your comments and/or suggestions would be appreciated. bob
wyman |
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