An Order-Based Theory of Updates for Closed Database Views
An Order-Based Theory of Updates for Closed Database Views
复制标题
封闭数据库视图的基于顺序的更新理论
DOI：
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发表时间：
2004
影响因子：
1.2
通讯作者：
S. Hegner
中科院分区：
文献类型：
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作者：
S. Hegner
数据库模式视图更新策略设计的基本问题是选择视图更新如何反映回基模式。这项工作提出了一个解决这个问题的方法，基于封闭更新策略和基于顺序的数据库映射的双重哲学。封闭更新策略是指整个更新集都表现出自然的封闭属性，包括传递性和可逆性。基于顺序的范式是一种自然的范式;大多数数据库形式主义赋予数据库状态一种自然的顺序结构，在这种结构下，通过插入进行更新是一种递增操作，而通过删除进行更新是递减操作。在增加原来的常量补充策略的Bancilhon和Spyratos -这是一个早期版本的封闭更新策略-与兼容的顺序为基础的概念，反映到基础架构的任何更新的视图模式，这是一个插入，删除，或修改，这是可实现的插入和删除序列被证明是唯一的和独立的选择的补充。除了这种独特性表征，本文还开发了一种理论，确定条件下，一个自然的，最大的，更新策略存在的看法。然后将该理论应用于一个普遍存在的例子-受等式生成依赖约束的单关系模式。在这个框架内，它示出，对于定义为投影的主要关系的视图，唯一的可能性是，补充定义的更新过程也是一个投影，并且重建是基于功能依赖。
The fundamental problem in the design of update strategies for views of database schemata is that of selecting how the view update is to be reflected back to the base schema. This work presents a solution to this problem, based upon the dual philosophies of closed update strategies and order-based database mappings. A closed update strategy is one in which the entire set of updates exhibit natural closure properties, including transitivity and reversibility. The order-based paradigm is a natural one; most database formalisms endow the database states with a natural order structure, under which update by insertion is an increasing operation, and update by deletion is decreasing. Upon augmenting the original constant-complement strategy of Bancilhon and Spyratos – which is an early version of a closed update strategy – with compatible order-based notions, the reflection to the base schema of any update to the view schema which is an insertion, a deletion, or a modification which is realizable as a sequence of insertions and deletions is shown to be unique and independent of the choice of complement. In addition to this uniqueness characterization, the paper also develops a theory which identifies conditions under which a natural, maximal, update strategy exists for a view. This theory is then applied to a ubiquitous example – single-relational schemata constrained by equality-generating dependencies. Within this framework it is shown that for a view defined as a projection of the main relation, the only possibility is that the complement defining the update process is also a projection, and that the reconstruction is based upon functional dependencies.