DITA-OT-DIR
DITA_OT_DIR refers to the default directory that is specified for your DITA Open Toolkit distribution in the . preferences page
For example, if you are using DITA-OT 4.1.2 that comes bundled with Oxygen XML Editor, the default directory is: [OXYGEN_INSTALL_DIR]/frameworks/dita/DITA-OT. You can also specify a custom directory.