The technology of virtual data warehouses catches more and more interests of people. In this paper,aQuery-Optimization Based Virtual Data Warehouse (QVDW)model is presented,which not only has all the advantagesthat a virtual data warehouse has,but also can change bottom layer data structures and the model itself according tousers' various query requests. The aim is to offer customized service to OLAP (on-line analysis processing)users.
Software architecture has changed the way of programming by shifting developers′ focus from lines-of-codeto coarser-grained architectureal elements and their interconneetion structure. Furthermore, a flexible architecturemakes it easier to identify and evolve the elements involved in a change. In this paper,we present a common messge-based framework which simplifies programming and is flexible to accommodate architecutral changes. A case studysuggests that our framework effectively aids in both program constructiong and software evolution.
