I've added a new section to the 4.0 Release Notes for tracking changes that impact backwards compatibility:
https://cwiki.apache.org/confluence/display/OOOUSERS/AOO+4.0+Release+Notes This would include changes to the public interfaces of AOO, including incompatible changes to API's (including spreadsheet functions), file formats, etc. I think we all acknowledge that a major release like 4.0 is an opportunity to make incompatible changes, but I hope we also agree that this is not a free-for-all where we can indiscriminately break compatibility. We need to think carefully about where we break compatibility, have good reasons for it, and have a plan for how we communicate such changes to users and application developers. The later, especially, need advance notice. Personally, I consider any changes that break compatibility to be "controversial" and think that lazy consensus should be sought on this list before committing it. Regards, -Rob