View Maintenance after View Synchronization

While current view technology assumes that the ISs do not change their schema, our Evolvable View Environment (EVE) project addresses this problem by evolving the view deenitions aaected by IS schema changes, which we coin view synchronization. In EVE, the view synchronizer rewrites the view deenitions by replacing view components with suitable components from other ISs. However, after such a view redeenition process, the view extents, if materialized, must also be brought up-to-date. In this paper, we propose strategies to address this incremental adaptation of the view extent after view synchronization. One key idea of our approach is to regard the complex changes done to a view dee-nition after synchronization as atomic unit. Second, to exploit knowledge of how the view deenition was synchronized, especially the containment information between the old and new view. Our techniques would successfully adapt views under the unavailability of base relations while currently known maintenance strategies from the literature would fail.