Created November 8, 2009
Last updated November 8, 2009
Normalization of classes
In this page , I will explan the normalization 1 2
of classes ( especially entity classes )3
The entity classes is the classes managing datas.
When you create the class diagram, I think that you pay attention to the module cohesion and coupling
At this time, When you normalize classes, new classes are likely extracted.
1:"normalization" is the same means as the normalization in RDB.
2:The normalization is a range of the Fundamental Information Technology Engineer Examination (FE) , the Software Design amp; Development Engineer Examination (SW) , the Database Systems Engineer Examination (DB) and so on of the Japan Information-Technology Engineers Examination
If you aim at passing , study it.
3:There are rew websites and books about object-oriented. I doubt that the authors of them understand object-oriented.
The normalization of the datas is the unification and integration of datas.
If you normalize datas , you can prevent datas not being adjusted, and lose the redundancy.
If you want to know the detail of the normalization , please refer to 1 of Reference.
Note:There is regularization from the 1NF to the 6NF. But you understand enough to from the 1NF to the 3NF.
Attention: There are the difference of the idea between RDB and object-oriented. For instance, assosication (see "Class diagram , Entity-relationship diagram and Extraction of the class") and operation (entity in RDB doesn't have it).
The following is examples. (Attention: "*" of "*NF" is posibility mistake.)
In this page , I explained only really easily for the regularization of datas.
- Aggregation and Composition
The aggregation and composition is result of 1NF( First Normal Form ).
- Flyweight pattern
I think that this class is extracted by 2NF or 3NF.
If you need , see the website at the following table.
I think that you should understand from the 1NF to the 3NF.
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