During the complex systems development, a great deal of data are generated from both the systems engineering process and project management process, and also some data are required to be prepared for the system engineering management plan (SEMP). For the successful completion of the project, it is necessary to effectively manage all the data in order to maintain data consistency and traceability. To fulfill the necessity, this paper introduces the concept of an integrated data architecture and discusses its realization with $Cradle^{(R)}$(a computer aided systems engineering tool). Also, it was described how to automate the production of the SEMP in that working environment. The result of the approach, managing complex data efficiently in the systems engineering view, has been successfully applied in the Railway Safety Development Program.