Remove COMPOSITION invariant preventing context for persistent Compositions
THis needs to be relaxed according to needs identified by implementers and described in
The only impact we can see is that applications and back-ends that treat COMPOSITION.context as prohibited for persistent COMPOSITIONs have to be adjusted to allow it to be optional.
There may be some impact on existing AQL queries that assume context can't exist on a persistent COMPOSITION.
Older data will remain valid with respect to the changed specification.
Change the EHR IM specfication to allow COMPOSITION.context to be non-Void for persistent COMPOSITIONs.
New NOTE in http://www.openehr.org/releases/RM/latest/docs/ehr/ehr.html#_occurrence_in_data replaces old statement that Persistent compositions did not have Event context.