<s>
In	O
computing	O
,	O
object	B-Application
model	I-Application
has	O
two	O
related	O
but	O
distinct	O
meanings	O
:	O
</s>
<s>
Examples	O
are	O
the	O
object	B-Application
models	I-Application
of	O
Java	B-Language
,	O
the	O
Component	B-Application
Object	I-Application
Model	I-Application
(	O
COM	O
)	O
,	O
or	O
Object-Modeling	B-Application
Technique	I-Application
(	O
OMT	O
)	O
.	O
</s>
<s>
Such	O
object	B-Application
models	I-Application
are	O
usually	O
defined	O
using	O
concepts	O
such	O
as	O
class	O
,	O
generic	O
function	O
,	O
message	O
,	O
inheritance	B-Language
,	O
polymorphism	B-Application
,	O
and	O
encapsulation	B-Application
.	O
</s>
<s>
There	O
is	O
an	O
extensive	O
literature	O
on	O
formalized	O
object	B-Application
models	I-Application
as	O
a	O
subset	O
of	O
the	O
formal	B-Application
semantics	I-Application
of	I-Application
programming	I-Application
languages	I-Application
.	O
</s>
<s>
A	O
collection	O
of	O
objects	O
or	O
classes	O
through	O
which	O
a	O
program	B-Application
can	O
examine	O
and	O
manipulate	O
some	O
specific	O
parts	O
of	O
its	O
world	O
.	O
</s>
<s>
In	O
other	O
words	O
,	O
the	O
object-oriented	B-Language
interface	B-Application
to	O
some	O
service	O
or	O
system	O
.	O
</s>
<s>
Such	O
an	O
interface	B-Application
is	O
said	O
to	O
be	O
the	O
object	B-Application
model	I-Application
of	O
the	O
represented	O
service	O
or	O
system	O
.	O
</s>
<s>
For	O
example	O
,	O
the	O
Document	B-General_Concept
Object	I-General_Concept
Model	I-General_Concept
(	O
DOM	B-General_Concept
)	O
is	O
a	O
collection	O
of	O
objects	O
that	O
represent	O
a	O
page	O
in	O
a	O
web	B-Application
browser	I-Application
,	O
used	O
by	O
script	B-Language
programs	O
to	O
examine	O
and	O
dynamically	O
change	O
the	O
page	O
.	O
</s>
<s>
There	O
is	O
a	O
Microsoft	B-Application
Excel	I-Application
object	B-Application
model	I-Application
for	O
controlling	O
Microsoft	B-Application
Excel	I-Application
from	O
another	O
program	B-Application
,	O
and	O
the	O
ASCOM	B-Application
Telescope	O
Driver	O
is	O
an	O
object	B-Application
model	I-Application
for	O
controlling	O
an	O
astronomical	O
telescope	O
.	O
</s>
<s>
An	O
object	B-Application
model	I-Application
consists	O
of	O
the	O
following	O
important	O
features	O
:	O
</s>
<s>
Interfaces	B-Application
An	O
interface	B-Application
provides	O
a	O
definition	O
of	O
the	O
signature	O
of	O
a	O
set	O
of	O
methods	O
without	O
specifying	O
their	O
implementation	O
.	O
</s>
<s>
An	O
object	O
will	O
provide	O
a	O
particular	O
interface	B-Application
if	O
its	O
class	O
contains	O
code	O
that	O
implement	O
the	O
method	O
of	O
that	O
interface	B-Application
.	O
</s>
<s>
An	O
interface	B-Application
also	O
defines	O
types	O
that	O
can	O
be	O
used	O
to	O
declare	O
the	O
type	O
of	O
variables	O
or	O
parameters	O
and	O
return	B-Language
values	I-Language
of	O
methods	O
.	O
</s>
<s>
Actions	O
An	O
action	O
in	O
object-oriented	B-Language
programming	I-Language
(	O
OOP	O
)	O
is	O
initiated	O
by	O
an	O
object	O
invoking	O
a	O
method	O
in	O
another	O
object	O
.	O
</s>
