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--- principles:high_cohesion [2012-12-17 22:45] – acronym christian
+++ principles:high_cohesion [2021-09-02 20:07] – old revision restored (2021-03-25 15:16) 65.21.179.175
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-===== Definition =====
+===== Principle Statement =====
 [[glossary:Cohesion]] in a [[glossary:module]] should be high.
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 Not adhering to this principle, i.e. having a low cohesion, means that one module has several unrelated or only loosely related responsibilities. A change in the requirements for one of these may thus also affect the others which would not be the case in a highly cohesive module.
+===== Strategies =====
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 ==== Specializations ====
-  * [[principles:Information Expert]]: Adhering to information expert means that a module only has responsibilities which belong together. So this increases cohesion.
+  * [[Information Expert]]: Adhering to information expert means that a module only has responsibilities which belong together. So this increases cohesion.
-  * [[principles:Constantine's Law]]
+  * [[Constantine's Law]]: Constantine's Law is just the combination of HC and LC.
 ==== Contrary Principles ====
-  * [[principles:Keep It Simple Stupid]]: Sometimes it is simpler to assign a minor unrelated responsibility to a module, which lowers the cohesion. On the other hand introducing a new module for the responsibility would be better in terms of cohesion but increases complexity as it increases the number of modules.
+  * [[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.
 ==== Complementary Principles ====
-  * [[principles:Low Coupling]]
+  * [[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.
-  * [[principles:Principle of Least Surprise]]
+  * [[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.
 ==== Principle Collections ====
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   * [[wp>Cohesion (computer science)]]
   * [[wiki>CouplingAndCohesion]]