1. A method for differential dynamic content delivery, the method comprising: providing a session document for a presentation, wherein the session document includes a session grammar and a session structured document; providing a session copy of a user profile including a user classification; creating a user classification instruction in dependence upon rules governing changes in a user classification in a session copy of a user profile; creating a presentation control instruction, including: receiving from a 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; receiving, from a presenter, the user classification instruction to change a user classification in the session copy of a user profile; receiving the presentation control instruction, wherein the presentation control instruction includes a presentation action identifier and optional parameters; changing the user classification in the session copy of a user profile in dependence upon the presenter's instruction; updating the session document, including identifying a presentation document for the presentation, the presentation document including a presentation grammar and a structured document having structural elements classified with classification identifiers; identifying a user for the presentation, the user having a session copy of a user profile comprising user classifications; and filtering the structured document in dependence upon the user classifications of the session copy of a user profile and the classification identifiers, wherein filtering the structured document comprises extracting, from the structured document, structural elements having classification identifiers corresponding to the user classifications of the session copy of a user profile; writing the extracted structural elements into the session structured document in the session document; and filtering the presentation grammar, in dependence upon the extracted structural elements, into a session grammar in the session document; selecting from the session structured document a classified structural element in dependence upon a user classification in the session copy of a user profile of a user in the presentation, the presentation action identifier, and the parameters received as part of the presentation control instruction; and presenting the selected structural element to the user.