<s>
CycL	B-Language
in	O
computer	B-General_Concept
science	I-General_Concept
and	O
artificial	B-Application
intelligence	I-Application
is	O
an	O
ontology	B-Language
language	I-Language
used	O
by	O
Doug	O
Lenat	O
's	O
Cyc	B-Language
artificial	B-Application
intelligence	I-Application
project	I-Application
.	O
</s>
<s>
There	O
is	O
a	O
close	O
variant	O
of	O
CycL	B-Language
known	O
as	O
MELD	O
.	O
</s>
<s>
The	O
original	O
version	O
of	O
CycL	B-Language
was	O
a	O
frame	O
language	O
,	O
but	O
the	O
modern	O
version	O
is	O
not	O
.	O
</s>
<s>
Rather	O
,	O
it	O
is	O
a	O
declarative	B-Language
language	I-Language
based	O
on	O
classical	O
first-order	O
logic	O
,	O
with	O
extensions	O
for	O
modal	O
operators	O
and	O
higher	B-Algorithm
order	I-Algorithm
quantification	I-Algorithm
.	O
</s>
<s>
CycL	B-Language
is	O
used	O
to	O
represent	O
the	O
knowledge	O
stored	O
in	O
the	O
Cyc	B-Language
Knowledge	O
Base	O
,	O
available	O
from	O
Cycorp	B-Language
.	O
</s>
<s>
The	O
source	O
code	O
written	O
in	O
CycL	B-Language
released	O
with	O
the	O
OpenCyc	O
system	O
is	O
licensed	O
as	O
open	O
source	O
,	O
to	O
increase	O
its	O
usefulness	O
in	O
supporting	O
the	O
semantic	O
web	O
.	O
</s>
<s>
CycL	B-Language
has	O
some	O
basic	O
ideas	O
:	O
</s>
<s>
The	O
truth	O
or	O
falsity	O
of	O
a	O
CycL	B-Language
sentence	O
is	O
context-relative	O
;	O
these	O
contexts	O
are	O
represented	O
in	O
CycL	B-Language
as	O
Microtheories	O
.	O
</s>
<s>
The	O
concept	O
names	O
in	O
Cyc	B-Language
are	O
known	O
as	O
constants	O
.	O
</s>
<s>
Facts	O
about	O
concepts	O
are	O
asserted	O
using	O
certain	O
CycL	B-Language
sentences	O
.	O
</s>
