<s>
The	O
Meta-Object	B-Application
Facility	I-Application
(	O
MOF	O
)	O
is	O
an	O
Object	B-Architecture
Management	I-Architecture
Group	I-Architecture
(	O
OMG	B-Architecture
)	O
standard	O
for	O
model-driven	B-Language
engineering	I-Language
.	O
</s>
<s>
Its	O
purpose	O
is	O
to	O
provide	O
a	O
type	O
system	O
for	O
entities	O
in	O
the	O
CORBA	B-Architecture
architecture	I-Architecture
and	O
a	O
set	O
of	O
interfaces	O
through	O
which	O
those	O
types	O
can	O
be	O
created	O
and	O
manipulated	O
.	O
</s>
<s>
The	O
official	O
reference	O
page	O
may	O
be	O
found	O
at	O
OMG	B-Architecture
's	O
website	O
.	O
</s>
<s>
MOF	O
was	O
developed	O
to	O
provide	O
a	O
type	O
system	O
for	O
use	O
in	O
the	O
CORBA	B-Architecture
architecture	I-Architecture
,	O
a	O
set	O
of	O
schemas	O
by	O
which	O
the	O
structure	O
,	O
meaning	O
and	O
behaviour	O
of	O
objects	O
could	O
be	O
defined	O
,	O
and	O
a	O
set	O
of	O
CORBA	B-Architecture
interfaces	O
through	O
which	O
these	O
schemas	O
could	O
be	O
created	O
,	O
stored	O
and	O
manipulated	O
.	O
</s>
<s>
The	O
most	O
prominent	O
example	O
of	O
a	O
Layer	O
2	O
MOF	O
model	O
is	O
the	O
UML	B-Language
metamodel	O
,	O
the	O
model	O
that	O
describes	O
the	O
UML	B-Language
itself	O
.	O
</s>
<s>
These	O
would	O
be	O
,	O
for	O
example	O
,	O
models	O
written	O
in	O
UML	B-Language
.	O
</s>
<s>
Beyond	O
the	O
M3-model	O
,	O
MOF	O
describes	O
the	O
means	O
to	O
create	O
and	O
manipulate	O
models	O
and	O
metamodels	O
by	O
defining	O
CORBA	B-Architecture
interfaces	O
that	O
describe	O
those	O
operations	O
.	O
</s>
<s>
Because	O
of	O
the	O
similarities	O
between	O
the	O
MOF	O
M3-model	O
and	O
UML	B-Language
structure	O
models	O
,	O
MOF	O
metamodels	O
are	O
usually	O
modeled	O
as	O
UML	B-Language
class	O
diagrams	O
.	O
</s>
<s>
A	O
supporting	O
standard	O
of	O
MOF	O
is	O
XMI	B-Language
,	O
which	O
defines	O
an	O
XML-based	O
exchange	O
format	O
for	O
models	O
on	O
the	O
M3-	O
,	O
M2-	O
,	O
or	O
M1-Layer	O
.	O
</s>
<s>
MOF	O
only	O
provides	O
a	O
means	O
to	O
define	O
the	O
structure	O
,	O
or	O
abstract	B-Application
syntax	I-Application
of	O
a	O
language	O
or	O
of	O
data	O
.	O
</s>
<s>
MOF	O
is	O
a	O
Domain	B-Language
Specific	I-Language
Language	I-Language
(	O
DSL	O
)	O
used	O
to	O
define	O
metamodels	O
,	O
just	O
as	O
EBNF	O
is	O
a	O
DSL	O
for	O
defining	O
grammars	O
.	O
</s>
<s>
In	O
short	O
,	O
MOF	O
uses	O
the	O
notion	O
of	O
MOF::Classes	O
(	O
not	O
to	O
be	O
confused	O
with	O
UML::Classes	O
)	O
,	O
as	O
known	O
from	O
object	B-Language
orientation	I-Language
,	O
to	O
define	O
concepts	O
(	O
model	O
elements	O
)	O
on	O
a	O
metalayer	O
.	O
</s>
<s>
MOF	O
may	O
be	O
used	O
to	O
define	O
object-oriented	B-Language
metamodels	O
(	O
as	O
UML	B-Language
for	O
example	O
)	O
as	O
well	O
as	O
non	O
object-oriented	B-Language
metamodels	O
(	O
as	O
a	O
Petri	B-Operating_System
net	I-Operating_System
or	O
a	O
Web	O
Service	O
metamodel	O
)	O
.	O
</s>
<s>
As	O
of	O
May	O
2006	O
,	O
the	O
OMG	B-Architecture
has	O
defined	O
two	O
compliance	O
points	O
for	O
MOF	O
:	O
</s>
<s>
In	O
June	O
2006	O
,	O
a	O
request	O
for	O
proposal	O
was	O
issued	O
by	O
OMG	B-Architecture
for	O
a	O
third	O
variant	O
,	O
SMOF	O
(	O
Semantic	O
MOF	O
)	O
.	O
</s>
<s>
The	O
variant	O
ECore	O
that	O
has	O
been	O
defined	O
in	O
the	O
Eclipse	B-Language
Modeling	I-Language
Framework	I-Language
is	O
more	O
or	O
less	O
aligned	O
on	O
OMG	B-Architecture
's	O
EMOF	B-Application
.	O
</s>
<s>
Another	O
related	O
standard	O
is	O
OCL	B-Language
,	O
which	O
describes	O
a	O
formal	O
language	O
that	O
can	O
be	O
used	O
to	O
define	O
model	O
constraints	O
in	O
terms	O
of	O
predicate	O
logic	O
.	O
</s>
<s>
QVT	B-Language
,	O
which	O
introduces	O
means	O
to	O
query	O
,	O
view	O
and	O
transform	O
MOF-based	O
models	O
,	O
is	O
a	O
very	O
important	O
standard	O
,	O
approved	O
in	O
2008	O
.	O
</s>
<s>
See	O
Model	B-Language
Transformation	I-Language
Language	I-Language
for	O
further	O
information	O
.	O
</s>
<s>
MOF	O
can	O
be	O
viewed	O
as	O
a	O
standard	O
to	O
write	O
metamodels	O
,	O
for	O
example	O
in	O
order	O
to	O
model	O
the	O
abstract	B-Application
syntax	I-Application
of	O
Domain	B-Language
Specific	I-Language
Languages	I-Language
.	O
</s>
<s>
Kermeta	B-Language
is	O
an	O
extension	O
to	O
MOF	O
allowing	O
executable	O
actions	O
to	O
be	O
attached	O
to	O
EMOF	B-Application
meta-models	O
,	O
hence	O
making	O
it	O
possible	O
to	O
also	O
model	O
a	O
DSL	O
operational	O
semantics	O
and	O
readily	O
obtain	O
an	O
interpreter	O
for	O
it	O
.	O
</s>
<s>
JMI	B-Language
defines	O
a	O
Java	O
API	O
for	O
manipulating	O
MOF	O
models	O
.	O
</s>
<s>
OMG	B-Architecture
's	O
MOF	O
is	O
not	O
to	O
be	O
confused	O
with	O
the	O
Managed	O
Object	O
Format	O
(	O
MOF	O
)	O
defined	O
by	O
the	O
Distributed	O
Management	O
Task	O
Force	O
(	O
DMTF	O
)	O
in	O
section	O
6	O
of	O
the	O
Common	O
Information	O
Model	O
(	O
CIM	O
)	O
Infrastructure	O
Specification	O
,	O
version	O
2.5.0	O
.	O
</s>
