A pragmatic tool named as ERwin for designing database system logical schema is discussed. With ERwin, the database system logical schema of high quality with minimum time and low cost can be reached.

• 阐述了一个用以开发数据库应用系统的实用工具ERwin，用它设计数据库的逻辑模型，能大大提高逻辑模型的质量，减少设计时间和费用。