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principles:low_coupling

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Low Coupling (LC)

Variants and Alternative Names

  • Loose Coupling

Context

Principle Statement

Coupling between modules should be low.

Description

A module should not interact with too many other modules. Furthermore if a module A interacts with another module B, this interaction should be loose, which means that A should not make too many assumptions about B.

Rationale

If a module A interacts with a module B, there is a certain dependency between these modules. When for example A uses a certain functionality of B, then A depends on B. A makes the assumption that B provides a certain service, and moreover it makes assumptions on how this service can be used (by which mechanism, which parameters, etc.). If one of these assumptions is not true anymore because B has changed for some reason, A also has to change. So the fewer dependencies there are, the less likely it is that A stops working and has to be changed.

Furthermore A makes many and detailed assumptions about B, there is also a high probability that A has to change despite only relying one one other module. This is because in such a case A also needs to change when only a certain detail of B changes.

But if coupling is low, there are only few assumptions between the modules which can be violated. This reduces the chance of ripple effects.

Strategies

Origin

Evidence

Relations to Other Principles

Generalizations

Specializations

Contrary Principles

  • Keep It Simple Stupid: Reducing the coupling often involves the use of complicated interaction patterns, indirections, etc.

Complementary Principles

Principle Collections

OOD Principle Language
General Principles
ML KISS MIMC DRY GP RoE
Modularization Principles
MP HC ECV
Module Communication Principles
TdA/IE LC DIP
Interface Design Principles
EUHM PLS UP
Internal Module Design Principles
IH/E IAP LSP PSU

Example

Description Status

Further Reading

principles/low_coupling.1358245032.txt.gz · Last modified: 2013-05-20 12:45 (external edit)