No one would argue that EMP is not key preserved in a join to DEPT - given the correct primary/foreign keys in place.
Can the application insert/update on a VIEW as it will be very complex to code and change the application at this point of time. The database knows that x (the attribute) and 'X' the constant are the same in this case. I have Never used INSTEAD Of trigger and hope you can illustriate some example on the above case to take it forward. For example: A table contain 2 columns and i am running select query for a particular condn. The third query is the same as the second for that fact. I'm going to learn more about workspace manager and test it. We already do this (and more) Tom, It's optimistic that we choose the right way to maintain inherited history model (views and "instead of" triggers) in our solution - the same as Oracle in version-enable tables.