Public Emergency Warning Systems should support:

•   multiple recipients,
•   multiple channels,
•   multiple hazards,
•   multiple stakeholder groups,
•   multiple senders,
•   multiple platforms / applications and;
•   write-once message inputwrite-once message input;

while,

•   minimizing complexity of operation,
•   facilitating authorisation and coordination of messages,
•   preserving consistency of messages, and
•   minimizing cost of maintenance and development.