What is a ODM file
The OpenDocument Master Document file ODM and other, related files are XML-based file formats for various file types such as spreadsheets, charts, presentations and word processing documents, much like Microsoft Office programs. The purpose of OpenDocument is to allow users access to open formats for XML-based file formatting for use in office applications; giving an alternative to Microsoft Office. ODM files make it easier to share and send files from office programs. Master documents such as those with the ODM file extension are useful for taking pieces of information and different file types and placing them into one large document, such as a book.
Standards were developed by the OASIS consortium and Sun Microsystem specifications under the ISO/IEC 26300:2006/AMD 1:3023 standards. ODM files are the master documents of the Open Office suite. This allows subdocuments to be linked (ODT files linked with each other, creating an ODM file). This is useful for large documents such as books or large reports, but it can be less useful when seeking to edit small portions of the entire project or for printing and review of sections. Links are visible through options in the ODM file to allow users to alter, edit, remove, or view individual links and sections.
Here's a small, but not exhaustive list of programs that can open ODM documents: