A Relational Model of Data Large Shared Data Banks
A Relational Model of Data Large Shared Data Banks
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发表时间：
2000
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通讯作者：
F. E.
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作者：
F. E.
大型数据库的未来用户必须得到保护，不必知道数据在机器中是如何组织的（内部表示）。提供这种信息的提示服务不是令人满意的解决方案。当数据的内部表示发生变化时，甚至当外部表示的某些方面发生变化时，用户在终端和大多数应用程序上的活动应该不受影响。由于查询、更新和报告流量的变化以及存储信息类型的自然增长，经常需要更改数据表示。现有的非推理的格式化数据系统为用户提供了树结构的文件或稍微更通用的数据网络模型。在第一节中，这些模型的不足之处进行了讨论。介绍了一种基于n元关系的模型、数据库关系的范式和通用数据子语言的概念。在第2节中，讨论了对关系（而不是逻辑推理）的某些操作，并将其应用于用户模型中的冗余和一致性问题。
Future users of large data banks must be protected from having to know how the data is organized in the machine (the internal representation). A prompting service which supplies such information is not a satisfactory solution. Activities of users at terminals and most application programs should remain unaffected when the internal representation of data is changed and even when some aspects of the external representation are changed. Changes in data representation will often be needed as a result of changes in query, update, and report traffic and natural growth in the types of stored information. Existing noninferential, formatted data systems provide users with tree-structured files or slightly more general network models of the data. In Section 1, inadequacies of these models are discussed. A model based on n-ary relations, a normal form for data base relations, and the concept of a universal data sublanguage are introduced. In Section 2, certain operations on relations (other than logical inference) are discussed and applied to the problems of redundancy and consistency in the user's model.