A design method using a model is an effective approach for quickly judging whether a design is good or bad in response to requirements, and quick design decisions are an important point in the development cycle that aims to create value from the customer's point of view. On the other hand, the model Because it is intuitively easy to understand, it is created well in the new development process, but once a change is made, the model deteriorates and becomes difficult to maintain.This is not only necessary to maintain design quality when changing models, Possible change process issue. In this presentation, we will analyze the change request, specify the scope of change impact, and apply the derivative development technology to change and maintain the appropriate model by specifying the difference, which can contribute to quick design decisions. This section introduces points for maintaining design quality and examples of maintaining an appropriate model.