<s>
In	O
computer	B-General_Concept
science	I-General_Concept
,	O
the	O
role	B-Language
class	I-Language
model	I-Language
is	O
a	O
role	O
analysis	B-Language
pattern	I-Language
described	O
(	O
but	O
not	O
invented	O
)	O
by	O
Francis	O
G	O
.	O
Mossé	O
in	O
his	O
article	O
on	O
Modelling	O
Roles	O
.	O
</s>
<s>
Francis	O
G	O
.	O
Mossé	O
has	O
identified	O
5	O
role	O
analysis	O
patterns	O
that	O
can	O
be	O
used	O
to	O
solve	O
most	O
role	O
related	O
problems	O
:	O
Role	O
Inheritance	B-Language
,	O
Association	O
Roles	O
,	O
Role	O
Classes	O
,	O
Generalised	O
Role	O
Classes	O
and	O
Association	O
Class	O
Roles	O
.	O
</s>
<s>
A	O
solution	O
using	O
inheritance	B-Language
to	O
conceptualise	O
a	O
role	O
-	O
cf	O
.	O
</s>
<s>
the	O
Inheritance	B-Language
Role	O
Model	O
-	O
is	O
not	O
possible	O
,	O
as	O
this	O
would	O
allow	O
a	O
person	O
to	O
play	O
only	O
a	O
single	O
role	O
.	O
</s>
<s>
As	O
one	O
can	O
see	O
in	O
Figure	O
1	O
below	O
,	O
the	O
inheritance	B-Language
role	O
model	O
says	O
that	O
a	O
character	O
,	O
who	O
is	O
a	O
person	O
,	O
is	O
playing	O
in	O
a	O
film	O
.	O
</s>
<s>
Because	O
,	O
the	O
inheritance	B-Language
makes	O
a	O
character	O
a	O
person	O
in	O
general	O
,	O
not	O
a	O
particular	O
person	O
.	O
</s>
<s>
As	O
explained	O
in	O
Context	O
,	O
using	O
inheritance	B-Language
to	O
play	O
more	O
than	O
one	O
role	O
cannot	O
be	O
considered	O
,	O
because	O
a	O
class	O
could	O
not	O
play	O
two	O
roles	O
at	O
the	O
same	O
time	O
in	O
such	O
a	O
context	O
(	O
cf	O
.	O
</s>
<s>
the	O
Inheritance	B-Language
Role	O
Model	O
)	O
.	O
</s>
<s>
The	O
role	B-Language
class	I-Language
model	I-Language
provides	O
the	O
flexibility	O
of	O
the	O
association	O
with	O
role-specific	O
attributes	O
and	O
even	O
class	O
operations	O
,	O
if	O
needed	O
.	O
</s>
<s>
The	O
holder	O
UML	B-Language
role	O
becomes	O
a	O
dedicated	O
class	O
ContractHolder	O
with	O
these	O
specific	O
attributes	O
.	O
</s>
<s>
A	O
simple	O
application	O
of	O
the	O
role	B-Language
class	I-Language
model	I-Language
in	O
a	O
real	O
example	O
is	O
in	O
the	O
7th	O
art	O
(	O
see	O
Figure	O
3	O
)	O
,	O
the	O
cinematography	O
.	O
</s>
<s>
One	O
remark	O
easily	O
visible	O
is	O
that	O
not	O
all	O
the	O
role	O
needs	O
attributes	O
and	O
using	O
the	O
role	B-Language
class	I-Language
model	I-Language
for	O
all	O
of	O
them	O
is	O
unnecessary	O
(	O
like	O
for	O
the	O
Director	O
role	O
)	O
.	O
</s>
<s>
Redundancy	O
in	O
computer	B-General_Concept
science	I-General_Concept
means	O
more	O
work	O
in	O
maintenance	O
,	O
which	O
is	O
not	O
wished	O
.	O
</s>
<s>
The	O
analysis	B-Language
pattern	I-Language
"	O
Role	B-Language
Class	I-Language
Model	I-Language
"	O
offers	O
a	O
possibility	O
to	O
employ	O
a	O
model	O
with	O
linking	O
between	O
a	O
base	O
class	O
and	O
the	O
client	O
.	O
</s>
<s>
In	O
addition	O
inheritance	B-Language
is	O
not	O
a	O
part	O
of	O
the	O
solution	O
because	O
of	O
the	O
flexibility	O
of	O
zero	O
or	O
multiple	O
roles	O
(	O
role-specific	O
attributes	O
and	O
operations	O
)	O
.	O
</s>
<s>
The	O
problem	O
of	O
the	O
role	B-Language
class	I-Language
model	I-Language
is	O
the	O
redundancy	O
,	O
for	O
example	O
the	O
method	O
getName	O
is	O
visible	O
in	O
all	O
of	O
the	O
role	O
classes	O
described	O
in	O
Figure	O
4	O
.	O
</s>
