<s>
ObjVlisp	B-Language
is	O
a	O
1984	O
object-oriented	O
extension	O
of	O
Vlisp	O
–	O
Vincennes	O
LISP	O
,	O
a	O
LISP	O
dialect	O
developed	O
since	O
1971	O
at	O
the	O
University	O
of	O
Paris	O
VIII	O
–	O
Vincennes	O
.	O
</s>
<s>
It	O
is	O
noteworthy	O
as	O
one	O
of	O
the	O
earliest	O
implementations	O
of	O
the	O
concept	O
of	O
metaclasses	B-Language
,	O
and	O
in	O
particular	O
explicit	O
(	O
as	O
opposed	O
to	O
implicit	O
)	O
metaclasses	B-Language
.	O
</s>
<s>
In	O
the	O
ObjVlisp	B-Language
model	O
,	O
"	O
each	O
entity	O
is	O
an	O
instance	O
of	O
a	O
single	O
class	O
.	O
</s>
<s>
Classes	O
are	O
instances	O
of	O
other	O
classes	O
,	O
called	O
metaclasses	B-Language
.	O
</s>
<s>
ObjVlisp	B-Language
provided	O
a	O
far	O
more	O
flexible	O
metaclass	B-Language
model	O
than	O
that	O
provided	O
by	O
earlier	O
object-oriented	O
languages	O
,	O
especially	O
Smalltalk	B-Application
.	O
</s>
<s>
In	O
Smalltalk-80	B-Application
,	O
whenever	O
a	O
new	O
class	O
is	O
created	O
,	O
a	O
corresponding	O
metaclass	B-Language
is	O
created	O
automatically	O
;	O
it	O
does	O
not	O
have	O
a	O
name	O
independent	O
of	O
that	O
of	O
the	O
metaclass	B-Language
for	O
which	O
it	O
was	O
created	O
–	O
metaclasses	B-Language
are	O
implicit	O
rather	O
than	O
explicit	O
.	O
</s>
<s>
By	O
contrast	O
,	O
in	O
ObjVlisp	B-Language
,	O
it	O
is	O
possible	O
to	O
define	O
named	O
metaclasses	B-Language
,	O
and	O
when	O
defining	O
a	O
class	O
one	O
must	O
specify	O
which	O
named	O
metaclass	B-Language
it	O
will	O
instantiate	O
.	O
</s>
<s>
The	O
explicit	O
metaclass	B-Language
support	O
in	O
ObjVlisp	B-Language
influenced	O
the	O
provision	O
of	O
the	O
same	O
capability	O
in	O
the	O
Common	B-Application
Lisp	I-Application
Object	I-Application
System	I-Application
.	O
</s>
<s>
The	O
ObjVlisp	B-Language
object	O
model	O
was	O
later	O
implemented	O
in	O
Prolog	B-Language
to	O
produce	O
ObjVProlog	O
.	O
</s>
<s>
Both	O
Python	B-Language
and	O
Converge	O
implement	O
a	O
meta-class	O
system	O
that	O
is	O
equivalent	O
of	O
that	O
of	O
ObjVLisp	B-Language
.	O
</s>
