ALMAS13 — Semantics of undefined receivers

It is unclear whether it is an error condition to refer to a receiver before it has been registered or defined in a receiver hierarchy file. E.g. in an alert template configuration file, or when raising an alert (override or from data).
It is also unclear whether when registering a receiver it must match an entry in the hierarchy file.
It is also unclear whether it is permissible to call the LoadReceiverHierarchy multiple times and if so what semantics are expected.

Clarify Receiver Semantics

It is an error to refer to a receiver before it has been defined by load receiver hierarchy. (But receivers don't have to be registered - for instance a user with the relevant role may not have logged on to the system).
When registering a receiver it is an error for the receiver to not correspond to a hierarchy file entry.
Load receiver hierarchy may be invoked more than once per execution lifetime of ALMAS Manager, for instance by multiple producers to load a specific hierarchies for their needs. The semantics in this case are additive whilst disjoint: producers should define receivers in their own namespace; it is an error to define the same receiver in multiple hierarchies. Receiver instances may register themselves multiple times with receiver names from different producer namespaces.
Alternatively ALMAS Configuration maybe performed by a system function (entirely or in part). If entirely, the configuration operations are called once by the system function, producers don't invoke the configuration interface and receivers only register themselves once for the system defined receiver name.