规范封面和最小封面之间的区别 [英] Difference between canonical cover and minimal cover

问题描述

很抱歉，这是一个荒谬的问题；

Apologies if this is a ridiculous question;

我一直在高低寻找一个无济于事的答案。

I've searched high and low for an answer with no avail.

我知道如何计算最小覆盖率；

I know how to calculate minimal cover;

即确保每个功能依赖项在RHS上仅具有一个属性，
删除多余的/多余的通过计算检查所有FD的每个
的闭合来确定lhs属性，看看是否可以将其删除（再次通过计算闭合来计算）

ie ensure each functional dependency only has one attribute on the the RHS, remove extratraneous/redudant lhs attributes by calculating closure of each examining all FD's, seeing if any can be removed (again by calculating closure)

规范仅覆盖了另一个词

推荐答案

允许规范的覆盖在右侧具有多个属性。最低保障额不能。例如，规范封面可以是 A-> BC，而最小封面是 A-> B，A-> C。那是唯一的区别。

A canonical cover is "allowed" to have more than one attribute on the right hand side. A minimal cover cannot. As an example, the canonical cover may be "A -> BC" where the minimal cover would be "A -> B, A -> C". That is the only difference.

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