To simplify the task of constructing wrapperlmonitor for the information sources in data warehouse systems, we provide a modularized design method to reuse the code. By substituting some parts of wrapper modules, we can reuse the wrapper on a different information source. For each information source, we also deveIop a toolkit to generate a corresponding monitor. By the method, we can reduce much effort to code the monitor component. We also develop a method to map the object-relational schema into relational one. The mapping method helps us make an uniform interface between a wrapper and an integrator.