@zaitcev I usually think of views as something different, where you're not fundamentally changing what the stored data means, just how it's presented. This may not be the right view, especially if you get into computed views and so on. But even then it sort of feels like computed getters and setters in eg Python.
@zaitcev I guess my dividing line is 'do things that interpret the data without seeing your view explode, or can they still work correctly with what's there?' If the answer is no, I think that you have multiple (and incompatible) schemas, as people don't like about NoSQL.