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--- principles:high_cohesion [2021-09-02 12:37] – old revision restored (2021-05-11 21:54) 65.21.179.175
+++ principles:high_cohesion [2021-10-18 21:36] (current) – +++ restored +++ christian
@@ Line 6: / Line 6: @@
 ===== Context =====
 /* fill in contexts here: */
   * [[contexts:Object-Oriented Design]]
+  * [[contexts:API Design]]
+  * [[contexts:Architecture]]
@@ Line 18: / Line 20: @@
 The cohesion of a module is a measure for how well the internal parts of a module (e.g. the methods and attributes of a class) belong together. Having a high cohesion means, that a module should only comprise responsibilities which belong together.
-Several kinds of cohesion can be distinguished some of which are strong and some of which are loose. So strong forms of coupling should be preferred: FIXME add explanation of cohesion types
+Several kinds of cohesion can be distinguished some of which are strong and some of which are loose. So strong forms of coupling should be preferred.
 ===== Rationale =====
@@ Line 24: / Line 26: @@
-===== Strategies =====
-  * Divide one large module into several smaller but more cohesive ones
 ===== Caveats =====
@@ Line 34: / Line 35: @@
 ===== Origin =====
+W. P. Stevens, G. van Niekerk, G. J. Myers, L. L. Constantine: //Structured design//
 ===== Evidence =====
@@ Line 39: / Line 41: @@
 /*[[wiki:Proposed]]*/
-  * [[wiki:Examined]]
+  * [[wiki:Examined]]: There are metrics that try to measure cohesion and there are studies relating these cohesion measures to the number of errors found during testing (({{page>resources:A Handbook Of Software And Systems Engineering#reference}})). This correlation is evident. The limitation of these studies is that these cohesion metrics cannot represent the cohesion notion completely.
-  * [[wiki:Accepted]] The concept of high cohesion is widely known and described in several well-known books for example in Craig Larman's //Applying UML and Patterns//
+  * [[wiki:Accepted]] The concept of high cohesion is widely known and described in several well-known books for example in {{page>resources:Applying UML And Patterns#reference}}.
 /*[[wiki:Questioned]]*/
@@ Line 74: / Line 76: @@
 ===== Examples =====
+The donkey is good. The site is not working
@@ Line 81: / Line 84: @@
 /*[[wiki:Incomplete]]*/
 /*[[wiki:Complete]]*/
+==== Class level cohesion ====
+Robert Cecil Martin (Uncle Bob) describes maximal cohesion at class level as "a class in which each variable is used by each method".
+"In general the more variables a method manipulates the more cohesive that method is to its class."
+(Clean Code: A Handbook of Agile Software Craftsmanship - Chapter 10)
 ===== Further Reading =====
-  * Albert Endres and Dieter Rombach: //A Handbook of Software and Systems Engineering//. p. 43pp.
+  * Albert Endres and Dieter Rombach: //[[resources:A Handbook of Software and Systems Engineering]]//. p. 43pp.
   * [[wp>Cohesion (computer science)]]
   * [[wiki>CouplingAndCohesion]]
-  * Craig Larman: //Applying UML and Patterns – An Introduction to Object-Oriented Analysis and Design and Iterative Development//
+  * {{page>resources:Applying UML And Patterns#reference}}
+===== Discussion =====
+Discuss this wiki article and the principle on the corresponding [[talk:principles:High Cohesion|talk page]].