问题
The effectiveness of a "modularization" is dependent upon the criteria used in dividing the system into modules.
What I want is, suggest some criteria which can be used in decomposing a system into modules.
回答1:
Cohesion: the functionality in a module is related.
Low coupling: you have minimum dependencies between modules.
Coordinated lifecycle: changes to functionality within a module tends to occur at the same time. Usually a consequence of high cohesion.
回答2:
I think the Single Responsibility Principle would be a good guide. Try to define responsibilities for each modules, and make each module be responsible for its own thing.
See http://butunclebob.com/ArticleS.UncleBob.PrinciplesOfOod
回答3:
Interesting reading too: http://www.cs.umd.edu/class/spring2003/cmsc838p/Design/criteria.pdf
回答4:
It is very old question.
- Module is work assignment to a programmer or group of programmers. This also is the unit of change.
- Low coupling and cohesion are metrics for estimation quality of relationships between modules but they are not useful for decomposition.
- The decomposition should be made using "information hiding" as a criterion.
- Introduction with examples and description of process based on "information hiding" principle: http://www.sqrl.ul.ie/Downloads/Lecture2.pdf.
- State of art of this question is software product line topic.
来源：https://stackoverflow.com/questions/785441/how-to-decompose-a-system-into-modules