Re: [emergency-msg] Groups - CAP_DOM.pdf uploaded

[Art Botterell <acb@incident.com>]

Friends -

I've posted a simple object model diagram of a CAP message, based on 
the Working Group's latest draft.  As you'll see, it's a simple 
hierarchy of three types of elements:

- The <alert/> structure is the root element.  It provides basic 
information about the message itself: its source, its timing, its 
purpose and so on.  In the case of a "system" message (an "ack" or 
"error" or a cancellation of a prior message, for example) this 
element might exist by itself.  More often, though, it would include 
one or more <info/> elements.

- The <info/> structure is a complex element describes a hazard and 
recommends a response.  It may include links to supplemental 
information.  Multiple <info/> elements might exist to describe 
different aspects of the same event or hazard... e.g., different 
probabability or severity "bands" or different phases in time... or 
to provide versions of the same information in multiple languages. 
If an <info/> element is targeted to a particular geographic area, it 
would include one or more <area/> elements.

- The <area/> structure is a complex element that describes a 
geographic area and, optionally, an altitude or altitude band.  Each 
<alert/> element may include a free-text description and one 
prescriptive description (as a lat/lon polygon, point and radius, or 
using some arbitrary geographic code such as a FIPS code).  Multiple 
<alert/> elements might be used to describe the combination of 
multiple target areas for the <info/> element within which it occurs.

We'll drill into the particular components of each of these 
structures at the data dictionary level, but first I wanted to make 
sure we were all aligned about the object model in the abstract.

- Art