HL7 messages may contain:
a) data in a format suitable for display purposes (display-oriented data), or
b) data in a format which explicitly denotes field content (record-oriented)
This record-oriented data appears in two forms: tabular (defined in Section 2.15, "QUERIES," of this chapter); and application-message segment-oriented (defined in the various application sections of this document, see Chapters 3-12).
A display message can be generated to fit a variety of needs for unsolicited updates between systems. These are situations where the update information does not need to be captured by the receiving systems database, but only displayed, either on a visual medium (such as a PC, workstation or a CRT) or on printed medium.
The Unsolicited Display Message describes the display oriented message. It is the unsolicited version of the generalized Response display message (see Section 2.15, "QUERIES") It is acknowledged by a general acknowledgment message (ACK).
The content and format of record oriented messages require functionally specific capabilities. The technical committees responsible for functionally specific chapters define them within those chapters.