Hi XWiki devs I'd like to propose the following enhancement for the XWiki Migration Manager. This is the follow up proposal to this discussion <http://lists.xwiki.org/pipermail/devs/2015-February/058396.html>. The current idea is to merge the concepts of the Extension Manager and Migration Manager. Extensions should be able to provide individual data migrations to add the possibility of altering data relevant to this extension. These should be executed after installation or upgrade of an extension. Currently, the Migration Manager (still residing in the oldcore) does not support external migrations and only a version number for XWiki migrations is stored in the database. It has to be refactored (to it's own module?) and requires the functionality to store multiple version numbers with specific identifiers in the database for versioning migrations for individual extensions. We at the celements team <http://www.celements.ch/Home?language=en> have an interest in this functionality and are willing to carry and implement it. If you agree with the basic idea, I will start a design proposal document with more detailed information and possible challenges on http://design.xwiki.org WDYT? Marc synventis gmbh