I recently ran into a problem on a client system after applying an upgrade. When attempting to log into the Application Architect the login would get so far and then throw an error:
There is an error in XML document(0,0). (System.xml)
Root Elements is missing. (System.xml)
The resulting problem was discovered to be that the system was looking for a specific row in the VIRTUALFILESYSTEM. It was looking for it by the VirtualFielsystemID, which for some reason was not a correct ID. The row it was looking for was the one where the itemname=’modelindex.xml’ I was able to fix this by removing the row from the virtualfilesystem table for the modelindex:
delete from virtualfilesystem where itemname=’modelindex.xml’
After doing so the application architect re-opened. Rebuilding the platform will then regenerate that file.