ODM - OpenDocument Master Document is a file extension which was designed by OpenOffice.org. This extension works great because it supports the OpenDocument standard. You will be able to take advantage of this extension when it comes to saving links to external files which consists of the document content. There are master documents which allow multiple writers to work on different pieces of one large document at the same time. This comes in handy when you are writing books and even periodicals. Other large compilations are also handy for this type of extension. You will be able to access this download online.