The design and development of complex software systems is a difficult task, and it is not easy to ensure the quality of a developed software. The paper presents an architectural style-based approach to specifying and analyzing complex software systems. The approach is developed based on UML-like meta models and graph transformation techniques to support sound methodological principals, formal analysis and refinement. The approach is illustrated through the specification and simulation of architectural styles of mobile computing middleware, where three abstract levels of architectural styles are defined in order to decrease the complexity brought by mobility.