LINGUIST List 14.1593

Wed Jun 4 2003

Software: FSM and GRM libraries: Speech Recognition

Editor for this issue: Tomoko Okuno <>


  • Brian Roark, FSM and GRM libraries: Speech Recognition System

    Message 1: FSM and GRM libraries: Speech Recognition System

    Date: Tue, 03 Jun 2003 10:28:57 +0000
    From: Brian Roark <>
    Subject: FSM and GRM libraries: Speech Recognition System

    New versions (4.0) of the AT&T FSM and GRM libraries have been released, and binaries are available for research use.

    The FSM library is a set of general-purpose software tools for building, combining, optimizing, and searching weighted finite-state acceptors and transducers. Finite-state transducers are automata for which each transition has an output label in addition to the more familiar input label. Weighted acceptors or transducers are acceptors or transducers in which each transition has a weight as well as the input or input and output labels.

    The original goal of the FSM library was to provide algorithms and representations for phonetic, lexical, and language-modeling components of large-vocabulary speech recognition systems. This imposed the following requirements:

    Generality: to support the representation and use of the various information sources in speech recognition

    Modularity: to allow rapid experimentation with different representations

    Efficiency: to support competitive large-vocabulary recognition using automata of more than 10 million states and transitions.

    The GRM Library (Grammar Library) is a set of general-purpose software tools for constructing, modifying, and compiling grammars. It includes functions and utilities for:

    a. Context-Dependent Rewrite Rules: compilation of weighted context-dependent rules into weighted finite-state transducers defined over general semirings.

    b. Context-Free Grammars: approximation and compilation of weighted context-free grammars into weighted automata. Dynamic modification of compiled context-free grammar automata.

    c. Text and Grammar Processing Utilities: general text and grammar processing utilities (e.g., construction of weighted suffix automata, computation of the expected counts of sequences appearing in a weighted automaton, construction of local grammars).

    d. Statistical Language Models: creation and modification of statistical language models derived from text or weighted automata.

    The GRM library uses many of the functions and representations of the FSM library and outputs automata that can be directly manipulated with the FSM library.