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principles:high_cohesion [2013-03-18 09:44] – external edit 127.0.0.1principles:high_cohesion [2021-09-02 20:07] – old revision restored (2021-03-25 15:16) 65.21.179.175
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 ===== Strategies ===== ===== Strategies =====
- 
-  * Divide one large module into several smaller but more cohesive ones 
-===== Caveats ===== 
- 
-See section [[#contrary principles]]. 
  
  
 ===== Origin ===== ===== Origin =====
 +/* the *primary* source */
  
  
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 ==== Specializations ==== ==== Specializations ====
  
 +  * [[Information Expert]]: Adhering to information expert means that a module only has responsibilities which belong together. So this increases cohesion.
   * [[Constantine's Law]]: Constantine's Law is just the combination of HC and LC.   * [[Constantine's Law]]: Constantine's Law is just the combination of HC and LC.
-  * [[Single Responsibility Principle]] (SRP): SRP is a stronger version of HC. 
-  * [[Interface Segregation Principle]] (ISP): ISP is the application of HC to interfaces. 
  
 ==== Contrary Principles ==== ==== Contrary Principles ====
  
   * [[More Is More Complex]] (MIMC): Making a module highly cohesive often results in additional modules. Sometimes it is simpler to assign a minor unrelated responsibility to a module, which lowers the cohesion.   * [[More Is More Complex]] (MIMC): Making a module highly cohesive often results in additional modules. Sometimes it is simpler to assign a minor unrelated responsibility to a module, which lowers the cohesion.
-  * [[Model Principle]] (MP): Adhering to HC sometimes means to split up a class into several smaller ones which might correspond to the model less well. 
-  * [[Low Coupling]] (LC): A system consisting of one single module has a very low coupling as there are no dependencies on other modules. But such a system also has low cohesion. The other extreme, very many highly cohesive modules, naturally has a higher coupling between the modules. So here a compromise has to be found. 
  
  
 ==== Complementary Principles ==== ==== Complementary Principles ====
  
-  * [[Tell don't Ask/Information Expert]] (TdA/IE): IE may help finding solutions with high cohesion. On the other hand it may also be disadvantageous in some cases (see [[Tell don't Ask/Information Expert#caveats]]). +  * [[Low Coupling]] (LC): A system consisting of one single module has a very low coupling as there are no dependencies on other modules. But such a system also has low cohesion. The other extreme, very many highly cohesive modules, naturally has a higher coupling between the modules. So here a compromise has to be found.
   * [[Encapsulate the Concept that Varies]] (ECV): Adhering to HC often results in modules to be split up into several more cohesive ones. ECV gives further advice on how to do that.   * [[Encapsulate the Concept that Varies]] (ECV): Adhering to HC often results in modules to be split up into several more cohesive ones. ECV gives further advice on how to do that.
  
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-===== Examples =====+===== Example =====
  
  
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   * [[wp>Cohesion (computer science)]]   * [[wp>Cohesion (computer science)]]
   * [[wiki>CouplingAndCohesion]]   * [[wiki>CouplingAndCohesion]]
-  * Craig Larman: //Applying UML and Patterns – An Introduction to Object-Oriented Analysis and Design and Iterative Development// 
  
principles/high_cohesion.txt · Last modified: 2021-10-18 21:36 by christian