DBMS中泛化和专业化的区别

泛化和特化是增强实体关系图(EER-diagram)

1. 概括：
它的工作原理是自下而上的方法。在泛化中，较低级别的函数被组合成更高级别的函数，称为实体。进一步重复此过程以制作高级实体。

在泛化过程中，属性是从特定实体中提取的，因此我们可以创建泛化实体。我们可以总结泛化过程，因为它组合子类形成超类。

泛化示例 –
考虑两个实体学生和患者。这两个实体将具有自己的一些特征。例如，Student 实体将具有 Roll_No、Name 和 Mob_No，而患者将具有 PId、Name 和 Mob_No 特征。现在在这个例子中，Student 和 Patient 的 Name 和 Mob_No 可以组合为一个 Person 以形成一个更高级别的实体，这个过程称为泛化过程。

2. 专业化：
我们可以说专业化是泛化的对立面。在专业化中，事物被分解为更小的事物以进一步简化。我们也可以说，在专业化中，一个特定的实体被分成子实体，并根据它的特征来完成。在专业化继承中也会发生。

专业化的例子——
考虑一个实体帐户。这将有一些属性考虑它们 Acc_No 和 Balance。帐户实体可能有一些其他属性，如 Current_Acc 和 Savings_Acc。现在Current_Acc 可能有Acc_No、Balance 和Transactions，而Savings_Acc 可能有Acc_No、Balance 和Interest_Rate，此后我们可以说专门实体继承了更高级别实体的特征。

应用泛化和特化后，所得图形的结构是相同的。

泛化和专业化的区别：

GENERALIZATION	SPECIALIZATION
Generalization works in Bottom-Up approach.	Specialization works in top-down approach.
In Generalization, size of schema gets reduced.	In Specialization, size of schema gets increased.
Generalization is normally applied to group of entities.	We can apply Specialization to a single entity.
Generalization can be defined as a process of creating groupings from various entity sets	Specialization can be defined as process of creating subgrouping within an entity set
In Generalization process, what actually happens is that it takes the union of two or more lower-level entity sets to produce a higher-level entity sets.	Specialization is reverse of Generalization. Specialization is a process of taking a subset of a higher level entity set to form a lower-level entity set.
Generalization process starts with the number of entity sets and it creates high-level entity with the help of some common features.	Specialization process starts from a single entity set and it creates a different entity set by using some different features.
In Generalization, the difference and similarities between lower entities are ignored to form a higher entity.	In Specialization, a higher entity is split to form lower entities.
There is no inheritance in Generalization.	There is inheritance in Specialization.