Sequence Numbering

The HL7 protocol uses the sequence number protocol to avoid duplication of messages between sending and receiving systems. The HL7 Binding Component can either play the role of the service consumer (that is, the inbound service endpoint) or the service provider (that is, the outbound service endpoint). In both roles, it supports the sequence numbering protocol for HL7 message transactions.

The negotiation and incrementation of the sequence number is automatically performed by the binding component. The HL7 Binding Component receives the message with the sequence number from the external system, validates the message based on the excepted sequence number stored in the database, and sends a positive or negative acknowledgment with the expected sequence number back to the external system. Sequence numbering is enabled or disabled as an attribute of the HL7 protocolproperties WSDL element.