17. The system of claim 16 wherein the presentation control instruction is created by receiving from the first user participating in the presentation a key phrase and optional parameters for invoking a presentation action and parsing the key phrase and parameters against a voice response grammar into a presentation control instruction.
16. The system of claim 12 , wherein the presentation control instruction includes a presentation action identifier and optional parameters; and wherein the second classified structural element is selected in dependence upon the presentation action identifier and the parameters.