1. A method for transforming at least one data structure specifying at least one tree structure in a computing system to at least one modular finite state transducer (MFST), comprising: receiving at least one data structure specifying at least one tree structure representing at least one finite state transducer (FST) including action semantics for defining action information; and for any type of finite state machine (FSM) model represented by the at least one data structure, transforming the at least one data structure to at least one MFST while preserving the action information of the at least one data structure in the at least one MFST, wherein said transforming includes performing any of an intersection, union and complement operation, or performing any transformation operation that is reducible to any of an intersection, union and complement operation, on the at least one data structure, wherein it is determinable whether the resulting MFST accepts a non-empty input.