Currently, instances of FEEDER_AUDIT (common IM, "archetyped" package) can
be attached to any item in an openEHR structure, created due to imported
data. Each FEEDER_AUDIT instance includes a system_id attribute in order
to identify the source system. Originally, it was envisaged that if there
were other finer-grained ids could be included in the system_id, but this
is not very clear, and likely to be used on an ad hoc basis. A more structured
approach to identifiers in the originating and gateway systems is needed.