19. A computer program product for differential dynamic content delivery, the computer program product disposed in a signal bearing medium, the computer program product comprising 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.
19. A computer program product for differential dynamic content delivery, the computer program product disposed in a signal bearing medium, the computer program product comprising 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. 21. The computer program product of claim 19 , 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.