An episode can have one or many versions (but always at least one) with one of those marked as the “canonical” version. And a version always belongs to one and only one episode (actually versions can belong to clips too but let’s ignore that for a minute). Versions are probably the closest mapping in the model to media assets although the complications of delivering A/V online mean a version in iPlayer can have many different media files. And versions can have types. Aside from the canonical (default) version there might be versions with increased duration (the “repeat” of Desert Island Discs is longer), decreased duration (the LW version of the Today Programme) and, for TV, versions with BSL or audio description. So versions handle two aspects of change: editorial versioning (recuts) and accessibility versions.