====== Coupling ======
===== Meaning 1 =====

==== Alternative Terms ====
/*i.e. alternative names meaning the same thing*/


==== Definition ====
**Coupling** is a measure for the strength of the dependencies between modules.


==== Description ====

There are plenty of different types of couplings. These are the classic ones ordered from loose to tight((see G. J. Myers: //Reliable Software through Composite Design//)):
^   Type | Description | Justification |
^   [[No coupling]] | The modules do not know each other. | good |
^   [[Call coupling]] | A module calls another one. | good |
^   [[Data coupling]] | A module calls another one passing parameters to it. | good |
^   [[Stamp coupling]] | A module calls another one passing complex parameters to it. | good |
^   [[Control coupling]] | A module influences the control flow of another module. | bad or OK |
^   [[External coupling]] | The modules communicate using a simple global variable. | bad |
^   [[Common coupling]] | The modules communicate using a common global data structure. | bad |
^   [[Content coupling]] | A modules depends on the inner working of another module. This is the strongest form of coupling. | extremely bad |

Up to control coupling they can be considered "good" couplings, although the lower the coupling the better (see [[principles:Low Coupling]]).

Then there are also some special types of couplings:

^   [[Tramp Coupling]] | A module is only coupled to a data structure because some other module needs the data. The module gets the data and passes it to the other module without touching the “tramp data”((see M. Page-Jones: //The Practical Guide to Structured Systems Design//)) | bad |
^   [[Hybrid Coupling]] | A parameter (or return type) is data and control flow information at the same time. | partly bad |
^   [[Logical Coupling]] | A module makes some assumptions about another module without referencing it. For example a module A only sorts a list because some other module B which A technically does not know about needs it sorted. | bad |
^    [[Temporal Coupling]] |  | bad |
^    [[Natural Coupling]] | A natural coupling is a coupling between classes which represent concepts which are dependent in the same way. | good |
^    [[Artificial Coupling]] | An artificial coupling is a coupling which is only there for technical reasons. | bad |
^    [[patterns:Abstract Coupling]] | A design pattern using  | good |

==== Examples ====


==== Alternative Definitions ====
/*i.e. slightly different definitions for basically the same thing*/


==== See Also ====
  * [[Cohesion]]
  * [[principles:Low Coupling]]

==== Further Reading ====


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===== Other Meanings =====
/*i.e. the same term referring to something different; put short mentions here or better add more detailed descriptions as additional sections */

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===== Discussion =====

Discuss this wiki article and the term on the corresponding [[talk:glossary:Coupling|talk page]].