学生选课
........\学生选课.doc
........\概念模型
........\........\Conceptual Data Model 1.cdb
........\........\Conceptual Data Model 1.cdm
........\........\Conceptual Data Model 3.pdb
........\........\Conceptual Data Model 3.pdm
........\物理模型
........\........\PhysicalDataModel_1.pdm
........\........\PhysicalDataModel_4.pdm
........\........\数据库文件
........\........\..........\crebas.dat