<s>
Rule-based	B-General_Concept
machine	I-General_Concept
translation	I-General_Concept
(	O
RBMT	B-General_Concept
;	O
"	O
Classical	O
Approach	O
"	O
of	O
MT	O
)	O
is	O
machine	B-Application
translation	I-Application
systems	I-Application
based	O
on	O
linguistic	O
information	O
about	O
source	O
and	O
target	O
languages	O
basically	O
retrieved	O
from	O
(	O
unilingual	O
,	O
bilingual	O
or	O
multilingual	O
)	O
dictionaries	O
and	O
grammars	O
covering	O
the	O
main	O
semantic	O
,	O
morphological	O
,	O
and	O
syntactic	O
regularities	O
of	O
each	O
language	O
respectively	O
.	O
</s>
<s>
Having	O
input	O
sentences	O
(	O
in	O
some	O
source	O
language	O
)	O
,	O
an	O
RBMT	B-General_Concept
system	O
generates	O
them	O
to	O
output	O
sentences	O
(	O
in	O
some	O
target	O
language	O
)	O
on	O
the	O
basis	O
of	O
morphological	O
,	O
syntactic	O
,	O
and	O
semantic	B-General_Concept
analysis	I-General_Concept
of	O
both	O
the	O
source	O
and	O
the	O
target	O
languages	O
involved	O
in	O
a	O
concrete	O
translation	O
task	O
.	O
</s>
<s>
The	O
first	O
RBMT	B-General_Concept
systems	O
were	O
developed	O
in	O
the	O
early	O
1970s	O
.	O
</s>
<s>
The	O
most	O
important	O
steps	O
of	O
this	O
evolution	O
were	O
the	O
emergence	O
of	O
the	O
following	O
RBMT	B-General_Concept
systems	O
:	O
</s>
<s>
Today	O
,	O
other	O
common	O
RBMT	B-General_Concept
systems	O
include	O
:	O
</s>
<s>
There	O
are	O
three	O
different	O
types	O
of	O
rule-based	B-General_Concept
machine	I-General_Concept
translation	I-General_Concept
systems	O
:	O
</s>
<s>
Direct	O
Systems	O
(	O
Dictionary	B-General_Concept
Based	I-General_Concept
Machine	I-General_Concept
Translation	I-General_Concept
)	O
map	O
input	O
to	O
output	O
with	O
basic	O
rules	O
.	O
</s>
<s>
Transfer	O
RBMT	B-General_Concept
Systems	O
(	O
Transfer	B-General_Concept
Based	I-General_Concept
Machine	I-General_Concept
Translation	I-General_Concept
)	O
employ	O
morphological	O
and	O
syntactical	O
analysis	O
.	O
</s>
<s>
Interlingual	O
RBMT	B-General_Concept
Systems	O
(	O
Interlingua	B-General_Concept
)	O
use	O
an	O
abstract	O
meaning	O
.	O
</s>
<s>
RBMT	B-General_Concept
systems	O
can	O
also	O
be	O
characterized	O
as	O
the	O
systems	O
opposite	O
to	O
Example-based	O
Systems	O
of	O
Machine	B-Application
Translation	I-Application
(	O
Example	B-General_Concept
Based	I-General_Concept
Machine	I-General_Concept
Translation	I-General_Concept
)	O
,	O
whereas	O
Hybrid	O
Machine	B-Application
Translations	I-Application
Systems	O
make	O
use	O
of	O
many	O
principles	O
derived	O
from	O
RBMT	B-General_Concept
.	O
</s>
<s>
The	O
main	O
approach	O
of	O
RBMT	B-General_Concept
systems	O
is	O
based	O
on	O
linking	O
the	O
structure	O
of	O
the	O
given	O
input	O
sentence	O
with	O
the	O
structure	O
of	O
the	O
demanded	O
output	O
sentence	O
,	O
necessarily	O
preserving	O
their	O
unique	O
meaning	O
.	O
</s>
<s>
The	O
following	O
example	O
can	O
illustrate	O
the	O
general	O
frame	O
of	O
RBMT	B-General_Concept
:	O
</s>
<s>
The	O
RBMT	B-General_Concept
system	O
contains	O
:	O
</s>
<s>
The	O
RBMT	B-General_Concept
system	O
makes	O
use	O
of	O
the	O
following	O
:	O
</s>
<s>
Source	O
Mapping	O
Rules	O
which	O
indicate	O
how	O
syntactic	O
heads	O
and	O
grammatical	O
functions	O
in	O
the	O
source	O
language	O
are	O
mapped	O
onto	O
domain	O
concepts	O
and	O
semantic	O
roles	O
in	O
the	O
interlingua	B-General_Concept
;	O
</s>
<s>
Target	O
Mapping	O
Rules	O
which	O
indicate	O
how	O
domain	O
concepts	O
and	O
semantic	O
roles	O
in	O
the	O
interlingua	B-General_Concept
are	O
mapped	O
onto	O
syntactic	O
heads	O
and	O
grammatical	O
functions	O
in	O
the	O
target	O
language	O
;	O
</s>
<s>
This	O
makes	O
it	O
possible	O
to	O
create	O
translation	B-Application
systems	I-Application
for	O
languages	O
that	O
have	O
no	O
texts	O
in	O
common	O
,	O
or	O
even	O
no	O
digitized	O
data	O
whatsoever	O
.	O
</s>
<s>
Because	O
RBMT	B-General_Concept
systems	O
are	O
generally	O
built	O
from	O
a	O
strong	O
source	O
language	O
analysis	O
that	O
is	O
fed	O
to	O
a	O
transfer	O
step	O
and	O
target	O
language	O
generator	O
,	O
the	O
source	O
language	O
analysis	O
and	O
target	O
language	B-General_Concept
generation	I-General_Concept
parts	O
can	O
be	O
shared	O
between	O
multiple	O
translation	B-Application
systems	I-Application
,	O
requiring	O
only	O
the	O
transfer	O
step	O
to	O
be	O
specialized	O
.	O
</s>
<s>
Although	O
RBMT	B-General_Concept
systems	O
usually	O
provide	O
a	O
mechanism	O
to	O
create	O
new	O
rules	O
and	O
extend	O
and	O
adapt	O
the	O
lexicon	O
,	O
changes	O
are	O
usually	O
very	O
costly	O
and	O
the	O
results	O
,	O
frequently	O
,	O
do	O
not	O
pay	O
off	O
.	O
</s>
