결합도 (Coupling in Computer Science)

주제(Subject)
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한글(약어) : 결합도()
영어(약어) : coupling()


관련개념(Related Concepts)
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응집도,응집력(cohesion)
모듈화


개요(Summary)
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모듈 상호간에 의존하는 정도. 응집도가 모듈 내부의 요소간의 의존성을 표현하는 것에 비해, 결합도(coupling)는 모듈과 모듈 사이의 의존성 정도를 의미한다.


본문(Body)
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1. 모듈 상호간의 교환내용의 수준에 따른 분류(Source:Wikipedia:Coupling)

The types of coupling, in order of highest to lowest coupling, are as follows:

Content coupling (worst)
Content coupling is when one module modifies or relies on the internal workings of another module (e.g. accessing local data of another module). Therefore changing the way the second module produces data (location, type, timing) will lead to changing the dependant module.

Common coupling
Common coupling is when two modules share the same global data (e.g. a global variable). Changing the shared resource implies changing all the modules using it.

External coupling
External coupling occurs when two modules share an externally imposed data format, communication protocol, or device interface.

Control coupling
Control coupling is one module controlling the logic of another, by passing it information on what to do (e.g. passing a what-to-do flag).

Stamp coupling (Data-structured coupling)
Stamp coupling is when modules share a composite data structure and use only a part of it, possibly a different part (e.g. passing a whole record to a function which only needs one field of it). This may lead to changing the way a module reads a record because a field which the module doesn't need has been modified.

Data coupling
Data coupling is when modules share data through, for example, parameters. Each datum is an elementary piece, and these are the only data which are shared (e.g. passing an integer to a function which computes a square root).

Message coupling (low and best)
This is the loosest type of coupling. Modules are not dependent on each other, instead they use a public interface to exchange messages.

2. 간단한 다이어그램
(MS Office PowerPoint 2007로 작성한 아래의 그림은 작성하는 데에 10분도 채 걸리지 않았다.)

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다이어그램 PPT파일

모임,단체(Commutities)
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블로그,개인 홈페이지 등(Humanities)
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참고문서(References)
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* 한국어(Korean)
저자. 역자. "제목". 출판사. 출판년도. (ISBN:)

* 영어(English)
저자. 제목, 판, 출판사. 출판년도. (ISBN:)
1. Wikipedia : Coupling
   http://en.wikipedia.org/wiki/Coupling_%28computer_science%29

2. Appaserver's Development Methodology
   http://timriley.net/appahost/myers_cohesion_coupling.html

3. Wikipedia : Loose Coupling
   http://en.wikipedia.org/wiki/Loose_coupling