Product line
Unity Pro, Control Expert

Resolution
The .XSY file is used to export and import variable files for use with Unity Pro. This file can be edited using XML Notepad 2007 by Microsoft.

As of Unity Pro V10, an Excel tool is provided that can be used to define/modify the exported XSY file in Excel. You can find the tool in the Unity Installation files \Extras\Excel Import Export Tool\ folder.