Proposal to add properties and relationships to Alarms

[cbupp]

Working through modeling BACnet and Niagara Edge Alarms, I'd like to propose:

• Alarm:
  • ADD sourcePoint relationship: Alarm should reference the Point/Points that are the source of the Alarm.
• Event
  • ADD eventIdentifier property: It's common for events to either generate a unique identifier, or use a reference number. This enables the events to be tracked and managed throughout it's lifecycle (important for ACK/clear on alarms)
  • ADD priority property: It's common for controller events to have an associated priority in order to understand how the system or operators should order their responses.
• ExceptionEvent
  • ADD fromState and toState properties: Common pattern I'm seeing on controllers is capturing both from and to state, not just the generated message.

I'm still working through with my teams how to capture acknowledge and clear of exception events, and plan to expand this PR. I'm also planning on capturing common alarm configurations (High limit, deadband, etc)

[PeteHart]

A question; the ExceptionEvent that is part of all alarms (as a lastKnownValue component) already includes a sourcePoint property so I don't understand why it's also needed on the Alarm itself?

Otherwise I'm ok with suggested changes.

[sn3kyJ3di]

Does source need to be so specific? An alarm might be generated by a device and not have any explicit point.