Office 2013 and Office 365 can open, edit and save both strict and transitional variants of ISO/IEC 29500. Office 2010 can handle transitional documents, but requires an add-on to open and edit the strict format, and can't save it, according to Microsoft's website. Office 2007 can't handle the strict variant at all. Office 2003 can open, edit and save only the transitional format, and for that requires an add-on.
Opting only for ODF risks alienating those citizens and businesses that either have no capability to read and edit ODF or who have already chosen to use Open XML as their default, Ferrar said.
However, even citizens using a version of Microsoft Office bought in the last seven years can handle ODF files. Office 2007 and 2010 can open and save ODF 1.1 files, while Office 2013 can open and edit ODF 1.1 and 1.2 files, although it can only save them as ODF 1.2, according to the Microsoft Office blog.
"By embracing both Open XML and ODF, the government can guarantee to reach the widest audience across both citizens and businesses without obliging either to expend money just to communicate with government," Ferrar wrote.
Even if citizens wanted OOXML documents, that wouldn't mean the government had to use Microsoft Office to generate them: LibreOffice, one of the two most popular packages built around the ODF file format, can read, edit and save documents in the OOXML format used by Microsoft Office 2007 and 2010 (transitional).
Ferrar also argued that iPad owners (of which there were 5.3 million in the U.K. in March 2013, according to YouGov) need additional software to display ODF files. While it is true that iPad users can view .docx files without additional software, they cannot edit them — which is problematic since Microsoft is proposing OOXML as an alternative to ODF for editable documents. The iPad, like most platforms today, can read PDF files, which the government proposes to use for documents that don't need editing.
In his response, Ferrar also claimed that Google Docs no longer supports ODF files, although in this reporter's tests the desktop version of the online productivity app can still import, edit and export ODF files.
Others are less enthusiastic than Ferrar about adopting both formats in parallel.
One such is Björn Lundell, an associate professor at the University of Skövde in Sweden, who has spent decades studying the development of computer file formats and their implementation in government and private sector software systems.
His view is that while adopting ODF makes sense, it would be unwise to put OOXML in any mandate.
The existence of several well-established open-source projects that can read and write ODF files helps minimize the risk of vendor lock-in, and promotes interoperability between software from different providers, including Microsoft Office, which can also handle ODF files, Lundell said.
Sign up for CIO Asia eNewsletters.