<s>
The	O
Common	B-Language
Algebraic	I-Language
Specification	I-Language
Language	I-Language
(	O
CASL	B-Language
)	O
is	O
a	O
general-purpose	O
specification	B-Application
language	I-Application
based	O
on	O
first-order	O
logic	O
with	O
induction	B-Algorithm
.	O
</s>
<s>
Partial	B-Algorithm
functions	I-Algorithm
and	O
subsorting	O
are	O
also	O
supported	O
.	O
</s>
<s>
CASL	B-Language
has	O
been	O
designed	O
by	O
CoFI	O
,	O
the	O
Common	O
Framework	O
Initiative	O
(	O
CoFI	O
)	O
,	O
with	O
the	O
aim	O
to	O
subsume	B-Architecture
many	O
existing	O
specification	B-Application
languages	I-Application
.	O
</s>
<s>
CASL	B-Language
comprises	O
four	O
levels	O
:	O
</s>
<s>
basic	O
specifications	B-Application
,	O
for	O
the	O
specification	O
of	O
single	O
software	O
modules	O
,	O
</s>
<s>
structured	O
specifications	B-Application
,	O
for	O
the	O
modular	O
specification	O
of	O
modules	O
,	O
</s>
<s>
architectural	B-Architecture
specifications	B-Application
,	O
for	O
the	O
prescription	O
of	O
the	O
structure	O
of	O
implementations	O
,	O
</s>
<s>
specification	O
libraries	O
,	O
for	O
storing	O
specifications	B-Application
distributed	O
over	O
the	O
Internet	O
.	O
</s>
<s>
In	O
particular	O
,	O
it	O
is	O
possible	O
to	O
use	O
CASL	B-Language
structured	O
and	O
architectural	B-Architecture
specifications	B-Application
and	O
libraries	O
with	O
logics	O
other	O
than	O
CASL	B-Language
.	O
</s>
<s>
This	O
feature	O
is	O
also	O
used	O
by	O
the	O
CASL	B-Language
extensions	O
.	O
</s>
<s>
Several	O
extensions	O
of	O
CASL	B-Language
have	O
been	O
designed	O
:	O
</s>
