<s>
Jess	B-Language
is	O
a	O
rule	O
engine	O
for	O
the	O
Java	B-Language
platform	O
that	O
was	O
developed	O
by	O
Ernest	O
Friedman-Hill	O
of	O
Sandia	O
National	O
Labs	O
.	O
</s>
<s>
It	O
is	O
a	O
superset	O
of	O
the	O
CLIPS	B-Application
programming	I-Application
language	I-Application
.	O
</s>
<s>
The	O
language	O
provides	O
rule-based	B-Language
programming	I-Language
for	O
the	O
automation	O
of	O
an	O
expert	B-Application
system	I-Application
,	O
and	O
is	O
frequently	O
termed	O
as	O
an	O
expert	B-Application
system	I-Application
shell	O
.	O
</s>
<s>
In	O
recent	O
years	O
,	O
intelligent	B-General_Concept
agent	I-General_Concept
systems	O
have	O
also	O
developed	O
,	O
which	O
depend	O
on	O
a	O
similar	O
capability	O
.	O
</s>
<s>
Rather	O
than	O
a	O
procedural	B-Application
paradigm	I-Application
,	O
where	O
a	O
single	O
program	O
has	O
a	O
loop	O
that	O
is	O
activated	O
only	O
one	O
time	O
,	O
the	O
declarative	B-Language
paradigm	I-Language
used	O
by	O
Jess	B-Language
continuously	O
applies	O
a	O
collection	O
of	O
rules	O
to	O
a	O
collection	O
of	O
facts	O
by	O
a	O
process	O
called	O
pattern	O
matching	O
.	O
</s>
<s>
Rules	O
can	O
modify	O
the	O
collection	O
of	O
facts	O
,	O
or	O
they	O
can	O
execute	O
any	O
Java	B-Language
code	I-Language
.	O
</s>
<s>
It	O
uses	O
the	O
Rete	B-Algorithm
algorithm	I-Algorithm
to	O
execute	O
rules	O
.	O
</s>
<s>
While	O
CLIPS	B-Application
is	O
licensed	O
as	O
open	B-Application
source	I-Application
,	O
Jess	B-Language
is	O
not	O
open	B-Application
source	I-Application
.	O
</s>
<s>
JESS	B-Language
is	O
free	O
for	O
educational	O
and	O
government	O
use	O
but	O
a	O
license	O
is	O
required	O
to	O
use	O
JESS	B-Language
for	O
commercial	O
systems	O
.	O
</s>
