The original goal of the AT&T FSM libraryTM 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 mathematical foundation of the library is the theory of rational power series, which supplies the semantics for the objects and operations and creates opportunity for optimizations such as determinization and minimization.