Specifies the identifier of a user who owns the current IModelDifference object.
A string which is the identifier of a user who owns the current model differences.
If the Security System is enabled, the SecuritySystem.CurrentUserId value is used as the identifier. If the Security System is disabled, the System.Security.Principal.WindowsIdentity.GetCurrent().Name value is used. If this property value is empty, then the current IModelDifference object specifies the model differences layer shared by all users (administrator model differences).