HL7 terms to better understand what is HL7. In the HL7 standard, the message type, RDE (Pharmacy/Treatment Encoded Order Message), is used by clinical applications to send an order to the pharmacy and/or dispensing systems. It may be sent as either an order containing a single pharmacy/treatment order for a patient or as an order containing multiple pharmacy/treatment orders for a patient (e.g., 1 mg tablet of Aspirin, 0.5 mg 0.5% Albuterol).
The transmission of orders occurs between the clinical application placing the order (the placer) and the clinical application filling the order (the filler). Typically, the clinician (e.g., physician) is entering orders on the HIS application which acts as the placer application in HL7 parlance. The system to which the order is targeted (e.g., the lab in the case of a complete blood count order) is the filler of the order.