Chameleon is used to set up the project configuration file that's used in Iguana, called a message definition file, or VMD for short. 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. Essentially, the VMD's main purpose is to act as the interface between Iguana and incoming/outgoing HL7 messages.