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The importance of acknowledgements (ACKs) in HL7 should not be understated. The only messages that should not be acknowledged are ACKs themselves (Acknowledging ACKs results in an infinite loop). Assuming delivery is not enough when clinical safety is at risk. A sending system user wants to know that their message has been successfully delivered and imported into the recipient system. An extension of this is human read acknowledgements indicating that the message content has been viewed.
ACKs also have other benefits such as highlighting how far in a delivery chain a message was transmitted before it failed, and thus which system to investigate the fault in. This implies that a sending system may receive multiple ACKs for a single message. Determining who the ACK originates from requires inspection of the sending facility and sending application. All actors in the chain of delivery have the potential to provide ACKs.
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