There are two basic international methods for development of ITS architecture: structural analysis method and object-oriented analysis method (The National ITS Architecture, 2001). No method is superior to the other, and both of them have their own characteristics. The structural analysis method is simple, clear and relatively mature. A complete set of specifications and standards has been generated for the method. The process-oriented analysis thought for the structured method relatively accords with the thinking habit of people and tends to be easily understood and accepted. Therefore, the structural analysis method is adopted in the study of intelligent transportation system supported by the new generation wireless communication technology (Jiang & Yang, 1999; ITS America, 1994).
The basic ideas of structural analysis method can be summarized as analytical hierarchy, functional modularization and correlation. The core of the method is top-down layer-by-layer decomposition and abstraction. The analysis procedures consist of three stages: requirements analysis, system model and physical model. The process of system analysis and construction is progressively described in such three stages (Wang, Qi, & Cai, 2004; Architecture Development Team, 2002; IBI Group, 2002; Bossom, 2000; System Architecture for ITS in Japan, 1999). These three stages respectively correspond to the user service definition, logical architecture and physical architecture of national ITS architecture, as shown in Figure 1.
The correspondence between structural analysis procedure and the dominant components of ITS architecture