One of the problems that plagues efforts to enable collaboration across editors is the fragility of the underlying markup. By that I mean that if I insert a new paragraph 3 at the same time you have transmitted a new paragraph 2, when both changes arrive, my intended location for paragraph 3 no longer exists. 

There are some character offset implementations that offer some "lite" markup but nothing approaching the richness of ODF.

I have recently posted a proposal to the change-tracking list at OASIS suggesting that a change in ODF change tracking could:

1) Enable auditability for all of the applications in the Libre Office suite,

2) Enable collaboration, whether with a central server, a workgroup or selected collaborators,

3) Enable authoring app flexibility, where an authoring app need only support the markup it where it will offer changes. 

All of those benefits arise from declaring an ODF document as immutable at the time of collaboration and/or change tracking.

Once it is treated as immutable, any application can reliably address the document using XPath for example, without conflict or the document changing due to another change.

For collaboration/change tracking, all changes should be written as XPath statements against the immutable original ODF document and stored as immutable statements themselves. The application, using its own internal run time model, projects the changes onto the document and enables the user to chose which changes to accept. (acceptance also being an XPath statement). If and when the user chooses to create a new version of the document, then the accepted changes are integrated with the original document and a new document is produced.

With the document and all changes being immutable, whether for graphic objects, documents and/or spreadsheets, each of those documents becomes an auditable record of the work. Such capabilities are available now, but only in very high end and specialized applications, such as: http://www.ibm.com/developerworks/aix/library/au-gpfs/index1.html.

Enabling small governments, businesses, individuals to have auditability, collaboration/change tracking and authoring flexibility would be a major step forward for a large number of users.

Hope everyone is having a great week!

Patrick