Thanks Ludovic for making this precise, I was under the exact same impression but feared I failed to know a newer technique. Composite objects (I think that's the practice here) is how sub-classing has been done in Curriki where, for example, attachments-assets are a special type of assets, with even more special types being zip archives, and SCORM packages. All these are just "added details" Curriki has also leveraged the custom-class feature, when an asset extends Document, and has implemented commodity methods based on that (e.g. "get the start resource of the zip"). Paul Le 26 août 2012 à 10:32, Ludovic Dubost a écrit :