Requirement: OpenDocument files versionning

[Pierre Ducroquet <pierre@ducroquet.info>]

+NAME
Pierre Ducroquet

+CONTACT
pierre@ducroquet.info

+CATEGORY (select one or more from below)
other

+SCOPE (select one or more from below)
general

+USE CASE
- An user want to store several versions of his document in a single file 
instead of relying on several copies on her file system.
- An user want to be able to go back to an older, specific document version.

+DESCRIPTION
That feature is already available in OpenOffice.org since at least the 2.0 
release, but it is not specified in OpenDocument 1.2
That implementation is totally independent from the OpenDocument standard, and 
if standardized, the versionned OpenDocument files would be 100% backward-
compatible.
This implementation does rely on a VersionList.xml file in the root of the 
document, and on a Versions sub-folder.
3 extra information are stored per version : the date time of the version, its 
creator and a comment.
The Versions sub-folder contains copies of the whole document, stored in zip 
files.
The main problem with that implementation is that it implies zip files stored in 
a zip file, which isn't really optimal.
We could maybe just use one sub-folder per version, and maybe consider a way to 
mark files as being used in more than one version.

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