FileInfo.com - The File Extensions Resource

.VDX File Extension

File Type	Visio Drawing XML File
File Format	File
Common?	No
File Description	Drawing or chart created with Microsoft Visio, a program for creating business diagrams and flowcharts; similar to a standard .VSD file, but saved in an XML format.
Program(s) that open vdx files	Windows: Microsoft Visio

Information from FileInfo.com - The File Extensions Resource.
http://www.fileinfo.com/extension/vdx