<s>
Helsinki	B-General_Concept
Finite-State	I-General_Concept
Technology	I-General_Concept
(	O
HFST	B-General_Concept
)	O
is	O
a	O
computer	O
programming	B-Library
library	I-Library
and	O
set	O
of	O
utilities	O
for	O
natural	O
language	O
processing	O
with	O
finite-state	B-Architecture
automata	I-Architecture
and	O
finite-state	B-Architecture
transducers	I-Architecture
.	O
</s>
<s>
It	O
is	O
free	B-License
and	I-License
open-source	I-License
software	I-License
,	O
released	O
under	O
a	O
mix	O
of	O
the	O
GNU	B-License
General	I-License
Public	I-License
License	I-License
version	O
3	O
(	O
GPLv3	B-License
)	O
and	O
the	O
Apache	B-Application
License	I-Application
.	O
</s>
<s>
The	O
library	B-Library
functions	I-Library
as	O
an	O
interchanging	O
interface	O
to	O
multiple	O
backends	O
,	O
such	O
as	O
OpenFST	O
,	O
foma	B-General_Concept
and	O
SFST	O
.	O
</s>
<s>
The	O
utilities	O
comprise	O
various	O
compilers	O
,	O
such	O
as	O
hfst-twolc	O
(	O
a	O
compiler	O
for	O
morphological	O
two-level	O
rules	O
)	O
,	O
hfst-lexc	O
(	O
a	O
compiler	O
for	O
lexicon	O
definitions	O
)	O
and	O
hfst-regexp2fst	O
(	O
a	O
regular	O
expression	O
compiler	O
)	O
.	O
</s>
<s>
Functions	O
from	O
Xerox	O
's	O
proprietary	O
scripting	O
language	O
xfst	O
is	O
duplicated	O
in	O
hfst-xfst	O
,	O
and	O
the	O
pattern	O
matching	O
utility	O
pmatch	O
in	O
hfst-pmatch	O
,	O
which	O
goes	O
beyond	O
the	O
finite-state	B-Architecture
formalism	O
in	O
having	O
recursive	B-Application
transition	I-Application
networks	I-Application
(	O
RTNs	O
)	O
.	O
</s>
<s>
The	O
library	B-Library
and	O
utilities	O
are	O
written	O
in	O
C++	B-Language
,	O
with	O
an	O
interface	O
to	O
the	O
library	B-Library
in	O
Python	B-Language
and	O
a	O
utility	O
for	O
looking	O
up	O
results	O
from	O
transducers	O
ported	O
to	O
Java	B-Language
and	O
Python	B-Language
.	O
</s>
<s>
Transducers	O
in	O
HFST	B-General_Concept
may	O
incorporate	O
weights	O
depending	O
on	O
the	O
backend	O
.	O
</s>
<s>
HFST	B-General_Concept
provides	O
two	O
native	O
backends	O
,	O
one	O
designed	O
for	O
fast	O
lookup	O
(	O
hfst-optimized-lookup	O
)	O
,	O
the	O
other	O
for	O
format	O
interchange	O
.	O
</s>
<s>
HFST	B-General_Concept
has	O
been	O
used	O
for	O
writing	O
various	O
linguistic	O
tools	O
,	O
such	O
as	O
spell-checkers	O
,	O
hyphenators	O
,	O
and	O
morphologies	O
.	O
</s>
<s>
Morphological	O
dictionaries	O
written	O
in	O
other	O
formalisms	O
have	O
also	O
been	O
converted	O
to	O
HFST	B-General_Concept
's	O
formats	O
.	O
</s>
