In (Bangalore Johnston and Banga-lore, 2005), we have shown that such grammars can be compiled into finite-state transducers enabling effective processing of lattice input from speech and gesture recognition and mutual compensation for errors and ambiguities.
like other approaches based on handcrafted grammars, multimodal grammars can be brittle with respect to extra-grammatical, erroneous and disfluent input.