Updating and inserting in views

Can anyone help . . . A question has come up regarding capabilities of views using Informix. A view is being used to prevent some using accessing particular columns in a table. What is the situation regarding updating records? Presumably, if the usual type of rules apply, to make sure there is an unambiguous mapping onto a row of the parent table, this is allowed. Is it possible to insert a record into the view? If so, what values to the columns that are not visible in the view take? Is it possible to modify this behaviour or do something similar with a trigger or a stored procedure (or whatever the Informix equivalent might be - I'm not terribly familiar with the specifics of Informix). Thanks for any help, Tony