Proposal: add <responseType> element in <info>

[Art Botterell <acb@incident.com>]

Some implementers have requested a consistently machine-readable 
coding for the response desired from the alert target audience.  As 
with <category> there appears to be no established all-hazard 
standard for this, but that doesn't mean we can't make a start.

We can address this requirement by adding a new, mandatory, 
enumerated element named <responseType> (or some such) within the 
<info> structure.  This element could be defined as "The code 
denoting the recommended response within the area addressed by this 
message."  The set of enumerated codes might include:

	Evacuate - Begin evacuation immediately.
	Prepare to Evacuate - Make preparations to evacuation and stand by.
	Shelter In Place - Take shelter and minimize exposure to the outdoors.
	Prepare to Shelter - Make preparations to shelter and stand by.
	Monitor News - Monitor news sources for further details and 
instructions.
	Mobilize - Activate pre-existing emergency plans.
	No action - Information only, no action required at this time.

Details and qualifications to these coded instructions would, of 
course, appear in the <instruction> element... this tag would be 
provided to direct automated systems to the appropriate processing... 
e.g., which siren signal, if any, to sound.

- Art