A GDTF file is a ZIP archive without compression which has the file extension *.gdtf.
A GDTF file consists of an XML file which contains the description and several resource files such as 3D model files and gobo images.
The ZIP archive contains a description.xml file and resource files. Some of the resource files are located in a folder structure. A characteristic GDTF file looks like this:
The GDTF file can be unzipped after changing the file extension to *.zip to inspect its content.