The header for a message exchange that is either requesting or responding to an action. The reference(s) that are the subject of the action as well as other information related to the action are typically transmitted in a bundle in which the MessageHeader resource instance is the first resource in the bundle.

MessageHeader
event[x]
Code for the event this message represents or link to event definition
destination
Message destination application(s)
name
Name of system
target
Particular delivery destination within the destination
endpoint
Actual destination address or id
receiver
Intended "real-world" recipient for the data
sender
Real world sender of the message
enterer
The source of the data entry
author
The source of the decision
source
Message source application
name
Name of system
software
Name of software running the system
version
Version of software running
contact
Human contact for problems
endpoint
Actual message source address or id
responsible
Final responsibility for event
reason
Cause of event
response
If this is a reply to prior message
identifier
Id of original message
code
ok | transient-error | fatal-error
details
Specific list of hints/warnings/errors
focus
The actual content of the message
definition
Link to the definition for this message