Separating this out is a design principle for Wagn 2.0.  In earlier wagns, there was only one namespace and only one card model based on active records, with related modules for revisions and extensions.  Extensions have all become pattern based hooks, and revisions still need to be handled in the card content model.  The active record model from wagn 1.x handles revisions as a array of raw content instances representing a linear sequence of updates for each card.  To support possible DeckoSystems and WagnClouds we need more clarity about all of this to support other systems and methods for change management in these contexts.