<s>
A	O
deductive	B-Language
language	I-Language
is	O
a	O
computer	B-General_Concept
programming	I-General_Concept
language	O
in	O
which	O
the	O
program	O
is	O
a	O
collection	O
of	O
predicates	O
( 	O
 '	O
facts	O
 '	O
)	O
and	O
rules	O
that	O
connect	O
them	O
.	O
</s>
<s>
Such	O
a	O
language	O
is	O
used	O
to	O
create	O
knowledge	B-General_Concept
based	I-General_Concept
systems	I-General_Concept
or	O
expert	B-Application
systems	I-Application
which	O
can	O
deduce	O
answers	O
to	O
problem	O
sets	O
by	O
applying	O
the	O
rules	O
to	O
the	O
facts	O
they	O
have	O
been	O
given	O
.	O
</s>
<s>
An	O
example	O
of	O
a	O
deductive	B-Language
language	I-Language
is	O
Prolog	B-Language
,	O
or	O
its	O
database-query	O
cousin	O
,	O
Datalog	B-Language
.	O
</s>
<s>
As	O
the	O
name	O
implies	O
,	O
deductive	B-Language
languages	I-Language
are	O
rooted	O
in	O
the	O
principles	O
of	O
deductive	O
reasoning	O
;	O
making	O
inferences	O
based	O
upon	O
current	O
knowledge	O
.	O
</s>
<s>
Deductive	B-Language
languages	I-Language
and	O
their	O
use	O
in	O
logic	B-Language
programming	I-Language
can	O
also	O
be	O
dated	O
to	O
the	O
same	O
year	O
when	O
Foster	O
and	O
Elcock	O
introduced	O
,	O
the	O
first	O
deductive/logical	O
programming	O
language	O
.	O
</s>
<s>
Shortly	O
after	O
,	O
the	O
first	O
Prolog	B-Language
system	O
was	O
introduced	O
in	O
1972	O
by	O
Colmerauer	O
through	O
collaboration	O
with	O
Robert	O
Kowalski	O
.	O
</s>
<s>
The	O
components	O
of	O
a	O
deductive	B-Language
language	I-Language
are	O
a	O
system	O
of	O
formal	O
logic	O
and	O
a	O
knowledge	O
base	O
upon	O
which	O
the	O
logic	O
is	O
applied	O
.	O
</s>
<s>
Although	O
first-order	O
logic	O
is	O
described	O
in	O
the	O
example	O
below	O
to	O
demonstrate	O
the	O
uses	O
of	O
a	O
deductive	B-Language
language	I-Language
,	O
no	O
formal	O
system	O
is	O
mandated	O
and	O
the	O
use	O
of	O
a	O
specific	O
system	O
is	O
defined	O
within	O
the	O
language	O
rules	O
or	O
grammar	O
.	O
</s>
<s>
Either	O
of	O
these	O
sentences	O
can	O
be	O
broken	O
down	O
into	O
predicates	O
which	O
can	O
be	O
compared	O
and	O
form	O
the	O
knowledge	O
base	O
of	O
a	O
deductive	B-Language
language	I-Language
.	O
</s>
<s>
A	O
collection	O
of	O
'	O
facts	O
 '	O
or	O
predicates	O
and	O
variables	O
form	O
the	O
knowledge	O
base	O
of	O
a	O
deductive	B-Language
language	I-Language
.	O
</s>
<s>
As	O
the	O
core	O
of	O
early	O
expert	B-Application
systems	I-Application
,	O
artificial	O
intelligence	O
systems	O
which	O
can	O
make	O
decisions	O
like	O
an	O
expert	O
human	O
,	O
knowledge	O
bases	O
provided	O
more	O
information	O
than	O
databases	B-Application
.	O
</s>
<s>
Prolog	B-Language
is	O
an	O
example	O
of	O
a	O
deductive	O
,	O
declarative	O
language	O
that	O
applies	O
first	O
-	O
order	O
logic	O
to	O
a	O
knowledge	O
base	O
.	O
</s>
<s>
To	O
run	O
a	O
program	O
in	O
Prolog	B-Language
,	O
a	O
query	O
is	O
posed	O
and	O
based	O
upon	O
the	O
inference	O
engine	O
and	O
the	O
specific	O
facts	O
in	O
the	O
knowledge	O
base	O
,	O
a	O
result	O
is	O
returned	O
.	O
</s>
