<s>
Object	B-Application
Oriented	I-Application
Analysis	I-Application
and	I-Application
Design	I-Application
models	O
are	O
often	O
presented	O
without	O
clarifying	O
the	O
viewpoint	O
represented	O
by	O
the	O
model	O
.	O
</s>
<s>
By	O
default	O
,	O
these	O
models	O
denote	O
an	O
implementation	O
viewpoint	O
that	O
visualises	O
the	O
structure	O
of	O
a	O
computer	B-Application
program	I-Application
.	O
</s>
<s>
Mixed	O
viewpoints	O
do	O
not	O
support	O
the	O
fundamental	O
separation	O
of	O
interfaces	B-Application
from	O
implementation	O
details	O
,	O
which	O
is	O
one	O
of	O
the	O
primary	O
benefits	O
of	O
the	O
object-oriented	B-Language
paradigm	O
.	O
</s>
<s>
In	O
Object	B-Application
Oriented	I-Application
Analysis	I-Application
and	I-Application
Design	I-Application
there	O
are	O
three	O
viewpoints	O
:	O
The	O
business	O
viewpoint	O
(	O
the	O
information	O
that	O
is	O
domain	O
specific	O
and	O
matters	O
to	O
the	O
end	O
user	O
)	O
,	O
the	O
specification	O
viewpoint	O
(	O
which	O
defines	O
the	O
exposed	O
interface	O
elements	O
of	O
a	O
class	O
)	O
,	O
and	O
the	O
implementation	O
viewpoint	O
(	O
which	O
deals	O
with	O
the	O
actual	O
internal	O
implementation	O
of	O
the	O
class	O
)	O
.	O
</s>
<s>
If	O
the	O
viewpoint	O
becomes	O
mixed	O
then	O
these	O
elements	O
will	O
blend	O
together	O
in	O
a	O
way	O
which	O
makes	O
it	O
difficult	O
to	O
separate	O
out	O
and	O
maintain	O
the	O
internals	O
of	O
an	O
object	O
without	O
changing	O
the	O
interface	O
,	O
one	O
of	O
the	O
core	O
tenets	O
of	O
Object	B-Application
Oriented	I-Application
Analysis	I-Application
and	I-Application
Design	I-Application
.	O
</s>
