One of the core philosophies of MobX is that the observable state should be as minimal as possible. Everything else should be derived via computed properties. This perspective makes sense when we talk about state management in UI. The UI is always nuanced on the same observable state and needs different views of the state depending on the context and task. This means that there are many possibilities for deriving a view-centric state (or representation) within the same UI.
An example of such a view-centric state is a table view and a chart view of the same list of observables. Both are operating on the same state but need different representations to satisfy the UI (the view) needs. Such representations are prime candidates for state derivations. MobX recognizes this core requirement and provides computed properties, which are specialized observables...