dc:title is filled according to the mime type of the file, and according
to the standard, xls and xlsx are different mime entries..xls
application/vnd.ms-excel .xlsx
application/vnd.openxmlformats-officedocument.spreadsheetml.sheetThis
will be similar for .doc and .docx, ppt and pptx
etc.https://blogs.msdn.microsoft.com/vsofficedeveloper/2008/05/08/office-2007-file-format-mime-types-for-http-content-streaming-2/Mark