Both Iguana and Chameleon make use of project configuration files. Each Iguana configuration file is edited using iNTERFACEWARE's Chameleon application. This file is referred to as a message definition file and has the extension .vmd.

The VMD file contains definitions for all the message definitions, segments, tables, composites, and mappings for a given project. The normal usage of Chameleon involves editing the VMD file to change the way that messages are parsed, generated, or transformed inside Iguana. The VMD's purpose is to act as the "interface" between Iguana and incoming/outgoing HL7 messages.

Iguana loads the VMD file and interacts with it to specify the following functions:

• Parsing logic;
• Table logic (database tables);
• Mapping logic; and
• Scripting logic.

	Any changes that are required to accommodate difference between alternate vendor's implementations and versions are configured using the message definition file. No changes are required in Iguana.