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Session Components

In the following, we list a couple of applications/components which may cooperate to form a distributed education session:

Audio/Video

Real-time audio/video streams may be multicast from the lecturer to the audience (lecture mode), from the audience to the lecturer (question/answer mode), and among the audience (discussion mode). The transmission of video information, while conceptually feasible also on the basis of public Internet infrastructure (MBONE), practically requires the use of dedicated connections (ISDN, ATM).

However, our experience shows [ATM96] that decent audio connections are much more important than video broadcasts because it is the voice which delivers the actual information contents of a lecture (provided that it is supported by the techniques presented below) while video usually just shows the lecturer's appearance. Fortunately audio can be transmitted in reasonable quality on generally available infrastructure (as demonstrated by the audio extensions of various WWW browsers).

Whiteboards

The core of highschool and university teaching is still the blackboard/whiteboard. "Electronic whiteboards" may deliver an adequate substitute for such kind of presentations using conventional desk-based pen-board devices³. The information content of such whiteboards can be transmitted to the audience locations using low-bandwidth connections (in contrast to video transmissions from physical boards). The same techniques may be also used in the other direction (students presenting at the whiteboard) but not all locations/host will in general be equipped with adequate input devices.

Electronic whiteboards are certainly required for various presentation modes (gradual developments of chains of reasoning) but in the context of virtual classrooms their role is that of a supplement rather than that of a core presentation technology.

Slide Shows

As he core of most virtual classroom presentations we expect the "slide show" i.e. sets of text documents augmented by images and possibly with animations. Slide shows may be developed manually, with various typesetting/word processing tools (SliTeX, MS Word) or with special presentation packages (MS Powerpoint). The rise of the WWW also suggests the use of HTML-based hypertext documents (potentially Java/JavaScript/ActiveX enhanced) for this purpose with the additional flexibility of crosslinking and hypertext navigation facilities and references to external resources.

The essential characteristics of slide shows is that they are available in electronic format⁴ and can be transmitted with comparatively little bandwidth requirements, possibly ahead of the session. However, for their presentation the lecturer needs explicit control/synchronization facilities (even for automatically running slide presentations, "start/stop/rewind" buttons are necessary). This requires interfacing with the corresponding viewers/browsers/interpreters, which may be easy (freeware available in source code), possible (WWW browser plugins, application with "dynamic linking" facilities), or hard to impossible ("closed-world" applications).

General Applications

A generalization of the rather straight-forward slide show is the integration of any kind of application programs into distributed education sessions. The selection and use of such systems depends on the particular education domain which makes their particular characteristics rather hard to predict. As an example, we therefore concentrate on the application of the computer algebra system Mathematica in mathematical education [Wol96] [Wol97].

The core of the system is an interpreter for the Mathematica programming language in which a large number of packages of mathematical algorithms have been implemented. Highly elaborated visualization features support the display of results in graphical form. Mathematica "notebooks" allows the typesetting of hypermedia documents that embed executable Mathematica code. "MathLink" allows (network) communication between Mathematica and external programs via serial channels.

A lecturer might use Mathematica simply in an interactive way, entering commands and running programs. The Mathematica window image should then be multicast to the audience. The lecturer might also prepare a Mathematica notebook and use the system as a presentation tool to display mathematical slides, possibly executing embedded Mathematica code. While it is also here possible to simply multicast the window image, a better use of network resources is to load the notebook on each participating host and invoke remote instances of Mathematica executing the local copies of the notebook. However, as described for slide shows, then synchronization with (or control by) the lecturer's presentation is required.

An even more advanced use of the system is possible, if the lecturer can switch control to the remote instances of Mathematica allowing the audience to run own test examples using the downloaded notebook ("exercise mode") and resume control when returning to presentation mode. For discussing questions and problems (see the next item), it would be also necessary to broadcast the particular screen image of a particular Mathematica invocation to lecturer and audience.

In a more general setting, the system might be also used in an "assessment mode" where questions are posed and results have to be computed/programmed/proved. These results have to be collected in stored for later retrieval from the lecturer.

Feedback

For use in education, it is also necessary to allow feedback from the audience. The simplest support could be a "raise hand" button that when pressed by some participant results in a message on the lecturer's screen. Having admitted the interruption, the participant may pose a question using a simple text-based interface, whiteboards, or audio/video. The question may be transmitted to the lecturer only or broadcast to all of the audience. More complex communication patterns (multi-user conferencing modes) might be supported as well; managing the complexity of such scenarios however represents a difficult task.

Autonomous Agents

Coordinating education sessions with a large audience in multiple locations may become soon to complex for the lecturer. Instead of installing separate floor managers, the use of autonomous agents may be investigated. Such agents may handle routine tasks that only require "semi-intelligent" reasoning capabilities but that put much strain on the lecturer: filtering streams of "raise hand" requests such that only one at a time is forwarded to the lecturer (using some scheduling heuristics and possibly blocking too many requests from single participants), handling session connection requests (using rules to decide which host may participate in which role), monitoring user activities and providing simple aid in "exercise mode", monitoring network connections and adjusting the quality of services or raising warnings, etc.