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principles:low_coupling [2013-03-03 11:04] – [Contrary Principles] RoE christianprinciples:low_coupling [2021-09-02 20:34] – old revision restored (2021-03-29 03:10) 65.21.179.175
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-===== Caveats ===== 
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-Coupling can be reduced by several technical measures (see [[#strategies]]). But while these measures reduce the coupling technically, they do not necessarily reduce the logical coupling. In such a case two modules A and B may seem decoupled, but ripple effects may occur anyway because of the logical coupling. In such a case it is better to make the coupling explicit by not applying a decoupling strategy. It may also be possible to find a better suitable strategy or a better way of applying the strategy to also get rid of the logical coupling. 
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-Furthermore note that coupling to a stable module is often no problem. The problematic cases are couplings to unstable modules. This means that applying decoupling strategies is beneficial when a coupling to an unstable module is reduced. But it may not be beneficial in the other cases. 
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-See also section [[#contrary principles]]. 
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 ===== Origin ===== ===== Origin =====
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 ==== Specializations ==== ==== Specializations ====
  
 +  * [[Tell, don't Ask/Information Expert]] (TdA/IE): Adhering to the information expert principle leads to low coupling as there is less need to communicate with other modules to get the necessary information.
   * [[Constantine's Law]]: Constantine's Law is just the combination of the two principles LC and HC.   * [[Constantine's Law]]: Constantine's Law is just the combination of the two principles LC and HC.
   * [[Dependency Inversion Principle]] (DIP): LC aims at reducing the dependencies to other modules. One way to do so is to only depend on abstractions. DIP is about this aspect.   * [[Dependency Inversion Principle]] (DIP): LC aims at reducing the dependencies to other modules. One way to do so is to only depend on abstractions. DIP is about this aspect.
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   * [[Keep It Simple Stupid]] (KISS): Reducing the coupling often involves the use of complicated interaction patterns, indirections, etc.   * [[Keep It Simple Stupid]] (KISS): Reducing the coupling often involves the use of complicated interaction patterns, indirections, etc.
   * [[High Cohesion]] (HC): 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.   * [[High Cohesion]] (HC): 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.
-  * [[Rule of Explicitness]] (RoE): Direct communication typically has the disadvantage of a higher coupling. Indirection reduces coupling but creates implicit/indirect communication paths.+
 ==== Complementary Principles ==== ==== Complementary Principles ====
  
-  * [[Tell, don't Ask/Information Expert]] (TdA/IE): IE may help to reduce coupling. Although there are also contrary cases (see [[Tell, don't Ask/Information Expert#caveats]]). 
   * [[Model Principle]] (MP): LC aims at reducing the dependencies to other modules. So a module shall depend on only a few others. MP now tells which dependencies are allowed and which aren't.   * [[Model Principle]] (MP): LC aims at reducing the dependencies to other modules. So a module shall depend on only a few others. MP now tells which dependencies are allowed and which aren't.
   * [[Information Hiding/Encapsulation]] (IH/E): Higher forms of couplings (especially content couplings) break encapsulation.   * [[Information Hiding/Encapsulation]] (IH/E): Higher forms of couplings (especially content couplings) break encapsulation.
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   * [[wiki>CouplingAndCohesion]]   * [[wiki>CouplingAndCohesion]]
   * Martin Fowler: //[[http://martinfowler.com/ieeeSoftware/coupling.pdf|Reducing Coupling]]//    * Martin Fowler: //[[http://martinfowler.com/ieeeSoftware/coupling.pdf|Reducing Coupling]]// 
-  * Craig Larman: //Applying UML and Patterns – An Introduction to Object-Oriented Analysis and Design and Iterative Development//+
principles/low_coupling.txt · Last modified: 2021-10-18 21:49 by christian