4. The method of claim 1 further comprising receiving a presentation control instruction, wherein: the presentation control instruction includes a presentation action identifier and one or more optional parameters; and selecting a classified structural element includes selecting a classified structural element in dependence upon the presentation action identifier and the parameters.
4. The method of claim 1 further comprising receiving a presentation control instruction, wherein: the presentation control instruction includes a presentation action identifier and one or more optional parameters; and selecting a classified structural element includes selecting a classified structural element in dependence upon the presentation action identifier and the parameters. 5. The method of claim 4 wherein: the presentation control instruction includes a presentation action identifier and one or more optional parameters; and selecting a classified structural element includes selecting a classified structural element in dependence upon the presentation action identifier and the parameters.