12. A language model back-off method for controlling a user interface employing plural language models selected from the group consisting of N-words, N-characters and combinations thereof, comprising: using a plurality of probabilistic language models including a first language model and a second language model that provides a lower level of constraint than the first language model to constrain navigation of selectable user interface components; using said first language model to constrain navigation of selectable user interface input components each corresponding to a corresponding one of characters, so as to constrain the characters that a user is allowed to input; receiving user input and interpreting the user input to determine if a selection of a next character to be input is made of one or more user interface input components; if the selection is not made, determining whether conditions are met for backing off the language models employed to constrain navigation of the user interface input components; and if the conditions are met, backing off the plural language models to a lower level of constraint by favoring the second language model over the first language model.
12. A language model back-off method for controlling a user interface employing plural language models selected from the group consisting of N-words, N-characters and combinations thereof, comprising: using a plurality of probabilistic language models including a first language model and a second language model that provides a lower level of constraint than the first language model to constrain navigation of selectable user interface components; using said first language model to constrain navigation of selectable user interface input components each corresponding to a corresponding one of characters, so as to constrain the characters that a user is allowed to input; receiving user input and interpreting the user input to determine if a selection of a next character to be input is made of one or more user interface input components; if the selection is not made, determining whether conditions are met for backing off the language models employed to constrain navigation of the user interface input components; and if the conditions are met, backing off the plural language models to a lower level of constraint by favoring the second language model over the first language model. 19. The method of claim 12 , further comprising determining whether the conditions are met based on a time since a previous selection.