On the foundations of the universal relation model
On the foundations of the universal relation model
复制标题
普遍关系模型的基础
DOI：
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发表时间：
1984
期刊：
影响因子：
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通讯作者：
Moshe Y. Vardi
中科院分区：
文献类型：
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作者：
D. Maier;J. Ullman;Moshe Y. Vardi
通用关系模型旨在通过减轻用户在关系之间进行逻辑导航的需要来实现关系数据库中完全的访问路径独立性。我们澄清了它的假设，并探讨了实施它的方法。
通用关系模型的基本思想是将访问路径嵌入到属性名中。因此，属性名称必须扮演独特的“角色”。此外，它假设对于每一组属性，用户都有一个基本的关系。用户的查询引用这些基本关系而不是底层数据库。
两个根本不同的方法，普遍关系模型已采取。根据第一种方法，用户对数据库的视图是用户对其提出查询的一个或多个泛关系。第二种方法将模型视为具有查询处理能力，使用户无需指定逻辑访问路径。因此，虽然第一种方法为查询应答提供了指称语义，但第二种方法为查询应答提供了操作语义。我们调查这两种方法之间的关系。
The universal relation model aims at achieving complete access-path independence in relational databases by relieving the user of the need for logical navigation among relations. We clarify the assumptions underlying it and explore the approaches suggested for implementing it.
The essential idea of the universal relation model is that access paths are embedded in attribute names. Thus attribute names must play unique “roles.” Furthermore, it assumes that for every set of attributes there is a basic relationship that the user has in mind. The user's queries refer to these basic relationships rather than to the underlying database.
Two fundamentally different approaches to the universal relation model have been taken. According to the first approach, the user's view of the database is a universal relation or many universal relations, about which the user poses queries. The second approach sees the model as having query-processing capabilities that relieve the user of the need to specify the logical access path. Thus, while the first approach gives a denotational semantics to query answering, the second approach gives it an operational semantics. We investigate the relationship between these two approaches.