Coupling Between Objects ( )

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Coupling Between Objects ( )

Works with all instances of a common meta-model, regardless of whether they were produced with the Java or the UML front-end. The respective extends (Java) or generalization (UML) relations expressing the inheritance between two classes are mapped onto relations of type inheritance in the common meta-model (and the

specific view).

Handle

Description

Coupling Between Objects (

) is the number of other classes that a class is coupled to.

is only applicable to object-oriented systems.

Scope

Class

View

${V}^{CBO} = ({G}^{CBO}, {R}^{CBO})$

Grammar ${G}^{CBO} = (\{\textrm{class}^{CBO}, \textrm{method}^{CBO}\}, \emptyset, \textrm{class}^{CBO})$
Relations ${R}^{CBO} = \{\textrm{coupling}^{CBO} : \textrm{class}^{CBO} \times \textrm{class}^{CBO}\}$

Mapping $\alpha^{CBO}$ :

$\displaystyle \alpha^{CBO}(\textrm{Class})$	$\displaystyle \mapsto$	$\displaystyle \textrm{class}^{CBO}$
$\displaystyle \alpha^{CBO}(\textrm{IsDefinedInTermsOf})$	$\displaystyle \mapsto$	$\displaystyle \textrm{coupling}^{CBO}$
$\displaystyle \alpha^{CBO}(\textrm{IsParameterOf})$	$\displaystyle \mapsto$	$\displaystyle \textrm{coupling}^{CBO}$
$\displaystyle \alpha^{CBO}(\textrm{InheritsFrom})$	$\displaystyle \mapsto$	$\displaystyle \textrm{coupling}^{CBO}$
$\displaystyle \alpha^{CBO}(\textrm{IsOfType})$	$\displaystyle \mapsto$	$\displaystyle \textrm{coupling}^{CBO}$
$\displaystyle \alpha^{CBO}(\textrm{Accessess})$	$\displaystyle \mapsto$	$\displaystyle \textrm{coupling}^{CBO}$
$\displaystyle \alpha^{CBO}(\textrm{Invokes})$	$\displaystyle \mapsto$	$\displaystyle \textrm{coupling}^{CBO}$

Definition

The

value of a class $c \in class^{CBO}$ is defined as:

$\displaystyle CBO(c)$

$\displaystyle =$

$\displaystyle \left\vert succ(c, \textrm{coupling}^{CBO}) \backslash c \right\vert$

Scale

Absolute.

Domain

Integers $\in 0..\infty$ .

Highly Related Software Quality Properties

Re-Usability 2.4

is negatively influenced by coupling.

Understandability for Reuse 2.4.1:: Parts, which have a high (outgoing) efferent coupling may be highly inversely related to understandability, since they are using other parts of the system which need to be understood as well.
Understandability decreases with increasing CBO.
Attractiveness 2.4.4:: Parts that have a high (outgoing) efferent coupling may be highly inversely related to attractiveness, since they are using other parts of the system which need to be understood as well, and represent dependencies.
Attractiveness decreases with increasing CBO.

Maintainability 2.6

decreases with increasing CBO.

Analyzability 2.6.1:: Parts that have a high (outgoing) efferent coupling may be highly inversely related to analyzability, since they are using other parts of the system which need to be analyzed as well.
Analyzability decreases with increasing CBO.
Changeability 2.6.2:: Parts that have a high (outgoing) efferent coupling may be inversely related to changeability, since they are using other parts of the system which might need to be changed as well.
Changeability decreases with increasing CBO.
Stability 2.6.3:: Parts showing a high (outgoing) efferent coupling may be inversely related to stability, since they are using other parts of the system, which are can affect them.
Stability decreases with increasing CBO.
Testability 2.6.4:: Parts that have a high (outgoing) efferent coupling may be highly inversely related to testability, since they are using other parts of the system which increase the number of possible test paths.
Testability decreases with increasing CBO.

Portability 2.7

decreases with increasing CBO.

Adaptability 2.7.1:: Parts that have a high (outgoing) efferent coupling may be inversely related to adaptability, since they are using other parts of the system that might need to be adapted as well.
Adaptability decreases with increasing CBO.

Related Software Quality Properties

Functionality 2.1

is both negatively and positively influenced by coupling.

Interoperability 2.1.3:: Parts that have a high (outgoing) efferent coupling may be directly related to interoperability, since they are using/interacting with other parts of the system.
Interoperability might increase with increasing CBO.
Security 2.1.4:: Parts that have a high (outgoing) efferent coupling may be inversely related to security, since they can be affected by security problems in other parts of the system.
Security might decrease with increasing CBO.

Reliability 2.2

might decrease with increasing CBO.

Fault-tolerance 2.2.2:: Parts that have a high (outgoing) efferent coupling may be inversely related to fault-tolerance, since they can be affected by faults in other parts of the system.
Fault-Tolerance might decrease with increasing CBO.
Recoverability 2.2.3:: Parts that have a high (outgoing) efferent coupling may be inversely related to recoverability, since their data is distributed in other parts of the system making their recovery difficult.
Recoverability might decrease with increasing CBO.

Re-Usability 2.4

might decrease with increasing CBO.

Learnability for Reuse 2.4.2:: Parts that have a high (outgoing) efferent coupling may be inversely related to learnability, since they are using other parts of the system which need to be understood as well.
Learnability might decrease with increasing CBO.
Operability for Reuse - Programmability 2.4.3:: Parts having a high (outgoing) efferent coupling may be inversely related to learnability, since they are using other parts of the system, which represent dependencies.
Programmability might decrease with increasing CBO.

Efficiency 2.5

might decrease with increasing CBO.

Time Behavior 2.5.1:: Parts that have a high (outgoing) efferent coupling may be inversely related to time behavior, since they are using other parts of the system, thus execution during test or operation does not stay local, but might involve huge parts of the system.
Time behavior might get worse with increasing CBO.
Resource Utilization 2.5.2:: Parts that have a high (outgoing) efferent coupling may be inversely related to resource utilization, since they are using other parts of the system, thus execution during test or operation does not stay local, but might involve huge parts of the system.
Resource utilization might get worse with increasing CBO.

References

CBO is extensively discussed and validated in [5,6,7,3,14,2,1,11,12,10,4,21,17,19],
it is implemented in the VizzAnalyzer Metrics Suite.

Since

Compendium 1.0

Next: Change Dependency Between Classes Up: Coupling Previous: Afferent Coupling ( )