<s>
A	O
component	O
in	O
the	O
Unified	B-Language
Modeling	I-Language
Language	I-Language
represents	O
a	O
modular	B-Architecture
part	O
of	O
a	O
system	O
that	O
encapsulates	B-Application
the	O
state	B-Application
and	O
behavior	O
of	O
a	O
number	O
of	O
classifiers	B-Language
.	O
</s>
<s>
Its	O
behavior	O
is	O
defined	O
in	O
terms	O
of	O
provided	O
and	O
required	O
interfaces	B-Application
,	O
is	O
self-contained	O
,	O
and	O
substitutable	B-Application
.	O
</s>
<s>
A	O
number	O
of	O
UML	B-Language
standard	O
stereotypes	B-Language
exist	O
that	O
apply	O
to	O
components	O
.	O
</s>
<s>
A	O
component	O
has	O
an	O
external	O
and	O
internal	O
view	O
,	O
also	O
known	O
as	O
"	O
black-box	O
"	O
and	O
"	B-General_Concept
white-box	I-General_Concept
"	I-General_Concept
,	O
respectively	O
.	O
</s>
<s>
For	O
its	O
internal	O
view	O
,	O
there	O
are	O
private	O
properties	O
and	O
realizing	O
classifiers	B-Language
and	O
shows	O
how	O
external	O
behavior	O
is	O
realized	O
internally	O
.	O
</s>
<s>
A	O
component	O
may	O
be	O
replaced	O
at	O
design	B-Application
time	I-Application
or	I-Application
run-time	I-Application
by	O
another	O
if	O
and	O
only	O
if	O
their	O
provided	O
and	O
required	O
interfaces	B-Application
are	O
identical	O
.	O
</s>
<s>
This	O
idea	O
is	O
the	O
underpinning	O
for	O
the	O
plug-and-play	B-Device
capability	O
of	O
component-based	B-Architecture
systems	O
and	O
promotes	O
software	O
reuse	O
.	O
</s>
<s>
Larger	O
pieces	O
of	O
a	O
system	O
's	O
functionality	O
may	O
be	O
assembled	O
by	O
reusing	O
components	O
as	O
parts	O
in	O
an	O
encompassing	O
component	O
or	O
assembly	O
of	O
components	O
,	O
and	O
wiring	O
together	O
their	O
required	O
and	O
provided	O
interfaces	B-Application
.	O
</s>
<s>
A	O
component	O
acts	O
like	O
a	O
package	B-Language
for	O
all	O
model	O
elements	O
that	O
are	O
involved	O
in	O
or	O
related	O
to	O
its	O
definition	O
,	O
which	O
should	O
be	O
either	O
owned	O
or	O
imported	O
explicitly	O
.	O
</s>
<s>
Typically	O
the	O
classifiers	B-Language
related	O
to	O
a	O
component	O
are	O
owned	O
by	O
it	O
.	O
</s>
<s>
Components	O
of	O
a	O
system	O
are	O
modeled	O
by	O
means	O
of	O
component	B-Library
diagrams	I-Library
throughout	O
the	O
development	B-Application
life	I-Application
cycle	I-Application
and	O
successively	O
refined	O
into	O
deployment	O
and	O
run-time	O
.	O
</s>
