10. A system for differential dynamic content delivery, the system comprising a computer processing unit, a computer memory operatively coupled to the computer processing unit, the computer memory having disposed within it computer program instructions capable of: providing a session document for a presentation, wherein the session document includes a session grammar and a session structured document; selecting from the session structured document a classified structural element bearing a preview designation; providing a preview of the selected structural element to a prospective user participant; receiving from the prospective user participant an indication of interest in the selected structural element; and recording the presentation for the prospective user participant based on said indication of interest and on the prospective user participant not attending a presentation session.
12. The system of claim 10 , further comprising: performing a presentation control instruction based on said indication of interest and on the prospective user participant not attending the presentation session; wherein the presentation control instruction involves recording the presentation if the prospective user participant does not attend the presentation and if the selected structural element is presented during the presentation session.