以下关于数据字典的描述中，不正确的是
A．数据字典是系统分析阶段的工具
B．数据字典有助于改进分析人员和用户间的通信
C．数据字典是应用系统中数据库设计的基础
D．数据字典是系统物理模型的一个重要组成部分
参考答案：D
解析： 数据字典(Data Dictionary,DD) 是关于对数据流图中包含的所有元素的信息的集合。数据流图和数据字典共同构成系统的逻辑模型，没有数据流图则数据字典难以发挥作用，没有数据字典则数据流图就不严格。数据字典最重要的用途是作为分析阶段的工具。对数据流图的各种成分起注解、说明的作用，对系统分析中其他需要说明的问题进行定义和说明；为系统开发人员在系统分析、系统设计及系统维护过程中提供关于数据的描述信息。数据流图与数据字典共同构成系统的逻辑模型，两者是相辅相成，缺一不可的。
The universities are schools of education and research but the main reason for their existence is not in the knowledge taught to the students or in the opportunities for the economic or social ___50___ resulting from the research findings. The true function of a university is that it keeps the ___51___ between knowledge and the real life. It unites the students with ordinary life in a ___52___ way. The university passes on information, but it ___53___ the information imaginatively. Imagination is the driving force for the society’s future development. Students’ imagination is the very ___54___ every university should protect and encourage. A university which ___55___ to do so has no reason for existence. With imagination, knowledge is not only knowledge: it includes all possibilities. It’s no longer a ___56___ on students’ memory. It’s food for thought and ___57___ for creative inventions. Imagination is not ___58___ knowledge. Instead, it is a way leading to more knowledge. It works by thoroughly studying the current knowledge and then exploring every possibility about the knowledge. In the exploration, new knowledge ___59___. Imagination enables men to construct a new vision of the world and it adds ___60___ to life through endless possibilities. Imaginative people are restless all along. Youth is imaginative and if the university can help preserve this precious wealth, the power of imagination can ___61___ change the world. Besides, it should also be made clear that imagination won’t be most effective without necessary experience. The problem of the current world is that those who are imaginative have only little experience ___62___ those who are experienced have weak imaginations. The ___63___ left for the universities is to hold together these two factors for the whole human race to ___64___ greater development and happiness.
|