HFST

Helsinki Finite-State Technology (HFST) is a computer programming library and set of utilities for natural language processing with finite-state automata and finite-state transducers. It is free and open-source software, released under a mix of the GNU General Public License version 3 (GPLv3) and the Apache License.

Helsinki Finite-State Technology
Developer(s)HFST team
Initial release2008 (2008)
Stable release
3.15.4 / February 13, 2021 (2021-02-13)[1]
Repository
Written inC++, Python, Java
Operating systemCross-platform: Linux, Mac OS X, Windows
Platformx86
Available inEnglish
TypeFinite-state toolkit
LicenseGPLv3, part Apache
Websitehfst.github.io

Features

The library functions as an interchanging interface to multiple backends, such as OpenFST, foma and SFST. The utilities comprise various compilers, such as hfst-twolc (a compiler for morphological two-level rules),[2] hfst-lexc (a compiler for lexicon definitions) and hfst-regexp2fst (a regular expression compiler). Functions from Xerox's proprietary scripting language xfst is duplicated in hfst-xfst, and the pattern matching utility pmatch in hfst-pmatch, which goes beyond the finite-state formalism in having recursive transition networks (RTNs).

The library and utilities are written in C++, with an interface to the library in Python and a utility for looking up results from transducers ported to Java and Python.

Transducers in HFST may incorporate weights depending on the backend. For performing FST operations, this is currently only possible via the OpenFST backend. HFST provides two native backends, one designed for fast lookup (hfst-optimized-lookup), the other for format interchange. Both of them can be weighted.

Uses

HFST has been used for writing various linguistic tools, such as spell-checkers, hyphenators, and morphologies.[3][4] Morphological dictionaries written in other formalisms have also been converted to HFST's formats.[5]

See also

Notes
  1. "Releases · hfst/hfst". github.com. Retrieved 2021-04-12.
  2. "A Short History of Two-Level Morphology".
  3. "GitHub - flammie/Omorfi: Open morphology for Finnish". GitHub. 2019-02-23.
  4. "How to Configure and Optimise Spellers".
  5. "Helsinki Finite-State Technology - Browse /Resources at SourceForge.net".

References

Lindén, Krister; Axelson, Erik; Drobac, Senka; Hardwick, Sam; Kuokkala, Juha; Niemi, Jyrki; Pirinen, Tommi; Silfverberg, Miikka (2013). "HFST - A System for Creating NLP Tools". In Mahlow, Cerstin; Piotrowski, Michael (eds.). Systems and Frameworks for Computational Morphology. Systems and Frameworks for Computational Morphology. Communications in Computer and Information Science. Vol. 380. Humboldt-Universität in Berlin: Springer. pp. 53–71.

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