Use case: small in-house hospital systems that query patient demographics via SQL. The new PAS being implemented in the near future will only support query/response via HL7. SQL access is available but intended for reporting so up to 24 hours behind.
Probably the easiest option is to set up a database in Ensemble and keep it up to date via standard ADT feed. This is going to have quite a large footprint and has a risk of getting out of sync.