Each Chameleon project can also be referred to as a message definition file. The message definition file has the extension .vmd.

The VMD file contains definitions for all the composites, segments, messages, tables and mappings for a given project. The normal usage of Chameleon involves editing the message definition file to change the way that messages are parsed and mapped. Essentially, the VMD acts as the interface between your application's data objects and incoming/outgoing HL7 messages.

For Chameleon users building their own application, the VMD file is deployed with (and loaded by) the application. A Chameleon Engine object loads the VMD and your application interacts with it. The VMD file is also used to specify the following:

• Parsing logic;
• Table logic (application data structures);
• Mapping logic; and
• Scripting logic.

	Accommodating Different Vendor Implementations The changes required to accommodate differences between alternate vendor's implementations and versions can be configured in the message definition file. If you are using Chameleon to build your own application, no modification is required to the application source code. How are VMD Files Used in Iguana? To learn how VMD files are used in Iguana, see The Message Definition (VMD) File.