Now that you have the VMD file that generates the XML text, the next step is to create a VMD file to generate the HL7 version 3 message. To create this VMD file:

• In Chameleon, in the Toolbar, click New to create a new VMD file.
• From the Workspace menu, select Import Segments From Library.
• In the Import Segments From Library window, select the Import segments from a library radio button, and select HL7 2.6 from the list box. Click Next.
• In the list of segments, select MSH. Click Next and Finish to import the MSH segment into your VMD file.
• In the Toolbar, click Message. This creates a new message, named Message1, in the Workspace.
• In the Workspace, in the Message1 definition, double-click Message Grammar. The Message Grammar window appears.
• If it is not already there, drag the MSH segment from the Workspace to the Segment Grammar panel of the Message Grammar window.
• In the Toolbar, click Options. In the Options window, click the Special Messages tab.
• From the Default (unidentified message) list box, select Message1. This ensures that all incoming messages are processed by this message definition. Click OK to close the Options window.
• From the Chameleon menu, select Global Inbound Script. In the window that appears, type or copy the following Python script:

value = 'MSH' + value

This code is required because Chameleon expects all messages to start with an MSH segment, whereas the messages this VMD file will be receiving have been converted to XML data by the other VMD file.

• In the Workspace, in the Message1 definition, double-click Transformation Script.
• In the window that appears, type or copy the script in this file: v3cda_script.txt.
• In the Toolbar, select Transform. In the Transformation window, select the Scripted Transformation radio button.
• Save this VMD file.

The Transformation Script calls a function named V2toCDA() to generate the CDA output, which calls functions to create each section of the document in turn:

def V2toCDA(PlainDataXml):
	InMsg = xml.dom.minidom.parseString(PlainDataXml)
	v3 = BeginDocument()
	v3 += Header()
	v3 += typeID()
	v3 += id()
	v3 += code()
	v3 += effectiveTime()
	v3 += confidentialityCode()
	v3 += recordTarget(getItem(InMsg, "Patient", 0, "PatientFirstName"), getItem(InMsg, "Patient", 0, "PatientLastName"))
	v3 += author()
	v3 += custodian()
	v3 += Body()
	v3 += EndDocument()
	return v3

Each section of the document is generated by its own function. For example, the author section of the CDA document is generated by the author() function:

def author():
  value = '<author>\n'
  value += v3Indent(1) + '<time value="2000040714"/>\n'
  value += v3Indent(1) + '<assignedAuthor>\n'
  value += v3Indent(2) + '<id extension="KP00017" root="2.16.840.1.113883.19.5"/>\n'
  value += v3Indent(2) + '<assignedPerson>\n'
  value += v3Indent(3) + '<name>\n'
  value += v3Indent(4) + '<given>Robert</given>\n'
  value += v3Indent(4) + '<family>Dolin</family>\n'
  value += v3Indent(4) + '<suffix>MD</suffix>\n'
  value += v3Indent(3) + '</name>\n'
  value += v3Indent(2) + '</assignedPerson>\n'
  value += v3Indent(2) + '<representedOrganization>\n'
  value += v3Indent(3) + '<id root="2.16.840.1.113883.19.5"/>\n'
  value += v3Indent(2) + '</representedOrganization>\n'
  value += v3Indent(1) + '</assignedAuthor>\n'
  value += '</author>\n'
  return value

All of the other functions work the same way: they generate one specific section of an HL7 version 3 CDA document, using the supplied parameters to customize this message section.

	It is important to note that this Python module is not a HL7 version 3 CDA document generation engine. It can only produce one specific type of HL7 version 3 CDA document. However, you can use this technique to generate other HL7 version 3 CDA documents. To do this: Determine the format of the HL7 version 3 CDA document that you want to generate. Determine what data you need from your incoming messages. Modify the VMD file described in Creating a VMD File To Extract Information in XML to extract this data and generate an XML file containing the data. Update the Transformation Script to generate the desired HL7 version 3 CDA document, supplying the data from the XML file.

	For a copy of this VMD file, click this link: v3cda_generate.vmd.