<s>
In	O
software	B-General_Concept
engineering	I-General_Concept
,	O
coupling	B-Application
is	O
the	O
degree	O
of	O
interdependence	O
between	O
software	O
modules	B-Architecture
;	O
a	O
measure	O
of	O
how	O
closely	O
connected	O
two	O
routines	O
or	O
modules	B-Architecture
are	O
;	O
the	O
strength	O
of	O
the	O
relationships	O
between	O
modules	B-Architecture
.	O
</s>
<s>
Coupling	B-Application
is	O
usually	O
contrasted	O
with	O
cohesion	O
.	O
</s>
<s>
Low	B-Application
coupling	I-Application
often	O
correlates	O
with	O
high	O
cohesion	O
,	O
and	O
vice	O
versa	O
.	O
</s>
<s>
Low	B-Application
coupling	I-Application
is	O
often	O
thought	O
to	O
be	O
a	O
sign	O
of	O
a	O
well-structured	O
computer	O
system	O
and	O
a	O
good	O
design	O
,	O
and	O
when	O
combined	O
with	O
high	O
cohesion	O
,	O
supports	O
the	O
general	O
goals	O
of	O
high	O
readability	O
and	O
maintainability	O
.	O
</s>
<s>
The	O
software	O
quality	O
metrics	O
of	O
coupling	B-Application
and	O
cohesion	O
were	O
invented	O
by	O
Larry	O
Constantine	O
in	O
the	O
late	O
1960s	O
as	O
part	O
of	O
a	O
structured	O
design	O
,	O
based	O
on	O
characteristics	O
of	O
“	O
good	O
”	O
programming	O
practices	O
that	O
reduced	O
maintenance	O
and	O
modification	O
costs	O
.	O
</s>
<s>
Structured	O
design	O
,	O
including	O
cohesion	O
and	O
coupling	B-Application
,	O
were	O
published	O
in	O
the	O
article	O
Stevens	O
,	O
Myers	O
&	O
Constantine	O
(	O
1974	O
)	O
and	O
the	O
book	O
Yourdon	O
&	O
Constantine	O
(	O
1979	O
)	O
,	O
and	O
the	O
latter	O
subsequently	O
became	O
standard	O
terms	O
.	O
</s>
<s>
Coupling	B-Application
can	O
be	O
"	O
low	O
"	O
(	O
also	O
"	O
loose	B-Application
"	O
and	O
"	O
weak	O
"	O
)	O
or	O
"	O
high	O
"	O
(	O
also	O
"	O
tight	O
"	O
and	O
"	O
strong	O
"	O
)	O
.	O
</s>
<s>
Some	O
types	O
of	O
coupling	B-Application
,	O
in	O
order	O
of	O
highest	O
to	O
lowest	O
coupling	B-Application
,	O
are	O
as	O
follows	O
:	O
</s>
<s>
A	O
module	B-Architecture
here	O
refers	O
to	O
a	O
subroutine	O
of	O
any	O
kind	O
,	O
i.e.	O
</s>
<s>
Content	O
coupling	B-Application
(	O
high	O
)	O
Content	O
coupling	B-Application
is	O
said	O
to	O
occur	O
when	O
one	O
module	B-Architecture
uses	O
the	O
code	O
of	O
another	O
module	B-Architecture
,	O
for	O
instance	O
a	O
branch	O
.	O
</s>
<s>
This	O
violates	O
information	B-Application
hiding	I-Application
–	O
a	O
basic	O
software	O
design	O
concept	O
.	O
</s>
<s>
Common	O
coupling	B-Application
Common	O
coupling	B-Application
is	O
said	O
to	O
occur	O
when	O
several	O
modules	B-Architecture
have	O
access	O
to	O
the	O
same	O
global	O
data	O
.	O
</s>
<s>
External	O
coupling	B-Application
External	O
coupling	B-Application
occurs	O
when	O
two	O
modules	B-Architecture
share	O
an	O
externally	O
imposed	O
data	O
format	O
,	O
communication	O
protocol	O
,	O
or	O
device	O
interface	O
.	O
</s>
<s>
Control	O
coupling	B-Application
Control	O
coupling	B-Application
is	O
one	O
module	B-Architecture
controlling	O
the	O
flow	O
of	O
another	O
,	O
by	O
passing	O
it	O
information	O
on	O
what	O
to	O
do	O
(	O
e.g.	O
,	O
passing	O
a	O
what-to-do	O
flag	O
)	O
.	O
</s>
<s>
Stamp	O
coupling	B-Application
(	O
data-structured	O
coupling	B-Application
)	O
Stamp	O
coupling	B-Application
occurs	O
when	O
modules	B-Architecture
share	O
a	O
composite	O
data	O
structure	O
and	O
use	O
only	O
parts	O
of	O
it	O
,	O
possibly	O
different	O
parts	O
(	O
e.g.	O
,	O
passing	O
a	O
whole	O
record	O
to	O
a	O
function	O
that	O
needs	O
only	O
one	O
field	O
of	O
it	O
)	O
.	O
</s>
<s>
In	O
this	O
situation	O
,	O
a	O
modification	O
in	O
a	O
field	O
that	O
a	O
module	B-Architecture
does	O
not	O
need	O
may	O
lead	O
to	O
changing	O
the	O
way	O
the	O
module	B-Architecture
reads	O
the	O
record	O
.	O
</s>
<s>
Data	O
coupling	B-Application
Data	O
coupling	B-Application
occurs	O
when	O
modules	B-Architecture
share	O
data	O
through	O
,	O
for	O
example	O
,	O
parameters	O
.	O
</s>
<s>
Subclass	O
coupling	B-Application
Describes	O
the	O
relationship	O
between	O
a	O
child	O
and	O
its	O
parent	O
.	O
</s>
<s>
Temporal	O
coupling	B-Application
It	O
is	O
when	O
two	O
actions	O
are	O
bundled	O
together	O
into	O
one	O
module	B-Architecture
just	O
because	O
they	O
happen	O
to	O
occur	O
at	O
the	O
same	O
time	O
.	O
</s>
<s>
In	O
recent	O
work	O
various	O
other	O
coupling	B-Application
concepts	O
have	O
been	O
investigated	O
and	O
used	O
as	O
indicators	O
for	O
different	O
modularization	O
principles	O
used	O
in	O
practice	O
.	O
</s>
<s>
The	O
goal	O
of	O
this	O
type	O
of	O
coupling	B-Application
is	O
to	O
provide	O
a	O
run-time	O
evaluation	O
of	O
a	O
software	O
system	O
.	O
</s>
<s>
It	O
has	O
been	O
argued	O
that	O
static	O
coupling	B-Application
metrics	O
lose	O
precision	O
when	O
dealing	O
with	O
an	O
intensive	O
use	O
of	O
dynamic	O
binding	O
or	O
inheritance	O
.	O
</s>
<s>
In	O
the	O
attempt	O
to	O
solve	O
this	O
issue	O
,	O
dynamic	O
coupling	B-Application
measures	O
have	O
been	O
taken	O
into	O
account	O
.	O
</s>
<s>
This	O
kind	O
of	O
coupling	B-Application
considers	O
the	O
conceptual	O
similarities	O
between	O
software	O
entities	O
using	O
,	O
for	O
example	O
,	O
comments	O
and	O
identifiers	O
and	O
relying	O
on	O
techniques	O
such	O
as	O
latent	O
semantic	O
indexing	O
(	O
LSI	O
)	O
.	O
</s>
<s>
Logical	O
coupling	B-Application
(	O
or	O
evolutionary	O
coupling	B-Application
or	O
change	O
coupling	B-Application
)	O
exploits	O
the	O
release	O
history	O
of	O
a	O
software	O
system	O
to	O
find	O
change	O
patterns	O
among	O
modules	B-Architecture
or	O
classes	O
:	O
e.g.	O
,	O
entities	O
that	O
are	O
likely	O
to	O
be	O
changed	O
together	O
or	O
sequences	O
of	O
changes	O
(	O
a	O
change	O
in	O
a	O
class	O
A	O
is	O
always	O
followed	O
by	O
a	O
change	O
in	O
a	O
class	O
B	O
)	O
.	O
</s>
<s>
A	O
change	O
in	O
one	O
module	B-Architecture
usually	O
forces	O
a	O
ripple	O
effect	O
of	O
changes	O
in	O
other	O
modules	B-Architecture
.	O
</s>
<s>
Assembly	O
of	O
modules	B-Architecture
might	O
require	O
more	O
effort	O
and/or	O
time	O
due	O
to	O
the	O
increased	O
inter-module	O
dependency	B-Application
.	O
</s>
<s>
A	O
particular	O
module	B-Architecture
might	O
be	O
harder	O
to	O
reuse	O
and/or	O
test	O
because	O
dependent	O
modules	B-Architecture
must	O
be	O
included	O
.	O
</s>
<s>
marshaling	O
)	O
and	O
message	O
interpretation	O
(	O
which	O
might	O
be	O
a	O
reference	O
to	O
a	O
string	O
,	O
array	O
or	O
data	O
structure	O
)	O
,	O
which	O
require	O
less	O
overhead	O
than	O
creating	O
a	O
complicated	O
message	O
such	O
as	O
a	O
SOAP	B-Application
message	O
.	O
</s>
<s>
However	O
,	O
complex	O
messages	O
such	O
as	O
SOAP	B-Application
messages	O
require	O
a	O
parser	O
and	O
a	O
string	O
transformer	O
for	O
them	O
to	O
exhibit	O
intended	O
meanings	O
.	O
</s>
<s>
One	O
approach	O
to	O
decreasing	O
coupling	B-Application
is	O
functional	B-Algorithm
design	I-Algorithm
,	O
which	O
seeks	O
to	O
limit	O
the	O
responsibilities	O
of	O
modules	B-Architecture
along	O
functionality	O
.	O
</s>
<s>
Coupling	B-Application
increases	O
between	O
two	O
classes	O
A	O
and	O
B	O
if	O
:	O
</s>
<s>
Low	B-Application
coupling	I-Application
refers	O
to	O
a	O
relationship	O
in	O
which	O
one	O
module	B-Architecture
interacts	O
with	O
another	O
module	B-Architecture
through	O
a	O
simple	O
and	O
stable	O
interface	O
and	O
does	O
not	O
need	O
to	O
be	O
concerned	O
with	O
the	O
other	O
module	B-Architecture
's	O
internal	O
implementation	O
(	O
see	O
Information	B-Application
Hiding	I-Application
)	O
.	O
</s>
<s>
Systems	O
such	O
as	O
CORBA	B-Architecture
or	O
COM	B-Application
allow	O
objects	O
to	O
communicate	O
with	O
each	O
other	O
without	O
having	O
to	O
know	O
anything	O
about	O
the	O
other	O
object	O
's	O
implementation	O
.	O
</s>
<s>
Coupling	B-Application
and	O
cohesion	O
are	O
terms	O
which	O
occur	O
together	O
very	O
frequently	O
.	O
</s>
<s>
Coupling	B-Application
refers	O
to	O
the	O
interdependencies	O
between	O
modules	B-Architecture
,	O
while	O
cohesion	O
describes	O
how	O
related	O
the	O
functions	O
within	O
a	O
single	O
module	B-Architecture
are	O
.	O
</s>
<s>
Low	O
cohesion	O
implies	O
that	O
a	O
given	O
module	B-Architecture
performs	O
tasks	O
which	O
are	O
not	O
very	O
related	O
to	O
each	O
other	O
and	O
hence	O
can	O
create	O
problems	O
as	O
the	O
module	B-Architecture
becomes	O
large	O
.	O
</s>
<s>
Coupling	B-Application
in	O
Software	B-General_Concept
Engineering	I-General_Concept
describes	O
a	O
version	O
of	O
metrics	O
associated	O
with	O
this	O
concept	O
.	O
</s>
<s>
For	O
data	O
and	O
control	O
flow	O
coupling	B-Application
:	O
</s>
<s>
For	O
global	O
coupling	B-Application
:	O
</s>
<s>
For	O
environmental	O
coupling	B-Application
:	O
</s>
<s>
Coupling(C )	O
makes	O
the	O
value	O
larger	O
the	O
more	O
coupled	O
the	O
module	B-Architecture
is	O
.	O
</s>
<s>
If	O
a	O
module	B-Architecture
has	O
5	O
input	O
and	O
output	O
data	O
parameters	O
,	O
an	O
equal	O
number	O
of	O
control	O
parameters	O
,	O
and	O
accesses	O
10	O
items	O
of	O
global	O
data	O
,	O
with	O
a	O
fan-in	O
of	O
3	O
and	O
a	O
fan-out	O
of	O
4	O
,	O
</s>
