The HL7 message you generated in the previous step had no MessageControlID value in field 10 of the MSH segment. What if you were required to provide a value for this field? For instance, this field may need a value to serve as a unique ID for the message.

To accomplish this, you have two options:

• Populate this HL7 field in the same way the fields in the PID segment were populated: by mapping data directly out of a table somewhere in your database. However, since the MessageControlID is something that is really only relevant to the HL7 world, you may not want to include this ID in your database.

• An alternative approach is to use Python to set the MessageControlID inside the VMD file.

In this tutorial, you will use the second approach.