Are object views updatable?
It is easy to update an object view where every attribute maps back to a real column in a table. For views that derive some attributes by more complex techniques, such as CAST-MULTISET, INSTEAD-OF triggers can be used to do the updates. When such a view is updated (or inserted into or deleted from), rather than attempting to implicitly modify any base tables, the system simply invokes the INSTEAD-OF trigger specified for the view. You can encapsulate whatever update semantics you want in the trigger body.
