说明：  选定关系模型作为系统的数据模型，在概念模型的基础上设计合理的数据库文件结构，主要考虑规范化和实际应用需要，一般要求达到三范式(3NF)；如果需要降低范式时，应对冗余数据及适当的反规范化设计进行说明
(If you need to reduce the paradigm to deal with redundant data selected relational model design a reasonable database file structure as the data model of the system, on the basis of the conceptual model, the main consideration standardization and practical application needs generally required to achieve three paradigms (3NF) described and appropriate standardized design)