iNTERFACEWARE™ Inc.

Application Overview

Rather than examine the C++ code you generated in detail, this section will focus on a conceptual overview of the generated application. The generated application's main components are as follows:

• A new Engine class, HL7appEngine, which inherits from the Engine class, HL7Engine. This class overrides the msg<MessageName> method that is invoked by the parser when a message of type <MessageName> is received. The default implementation of this method simply prints each extracted data element to the screen. For this tutorial you will retain this default behavior. In practice, however, this is where you would put your message handling logic.
• A server object; this object listens on a specified network port. When a message is received, it instructs the Engine to parse the message. In addition, it automatically constructs an acknowledgment message (an 'ACK' message) and sends it back to the message originator. The sending of the ACK is required by the HL7 standard. For more information, see Auto ACKknowledgement.
• The server object also directs its server connection object to listen for messages on a particular port.

The generated application has been thoroughly documented to make its operation as clear as possible.

With this structure in mind, it can briefly be discussed how the following three requirements - (1) Accepts incoming HL7 messages from some source; (2) Extracts data into custom data structures; and (3) Performs some function with the data, such as submitting it to a database, comparing it to other data, etc. - are satisfied by this generated project:

• The capture of incoming messages is handled by the server object. The port on which it should listen is specified by the server object.
• The generation of the ACK message is handled by the server's auto-acknowledgment logic.
• The message processing logic is, by default, to print the extracted data to the screen, but this can and should be overridden by the logic dictated by your specific needs.

The project you generated is a working application, even without doing any programming yourselves. However it does not satisfy the requirements first laid out in the specifications. As such you still need to do the following:

• Since you want to receive messages on the same port from Acme Medical and Magic Health Systems Inc., you must use the sorting engine algorithm to identify which messages came from Acme Medical and which came from Magic Health Systems Inc.
• After adding another configuration, you must write some code that your application will use to switch between configurations.

The design options are explained in the next section.