Side-Effect-Free View Updates

A view is an un-instantiated relation. The contents of its instance depend on the view query and the instances of the base tables. For that reason, an update issued on the view cannot be directly applied on the view instance. Instead, it has to be translated into a series of updates on the base tables so that when the view query is applied again on the modified base table instances, the result of the view update command will be observed on the view instance. Unfortunately, it is not always possible to find an update translation such that the change observed on the view instance is the one and only the one specified by the view update command. When this happens for a view update translation, the translation is said to have no side-effects. To fully exploit the updateability power of views, it is desired to be able to find update translations that have no side-effects.