Overview

Screenshot

Supported Features

Workspace Paradigm

Status of development

Reliability Issues

Software Architecture

The dlb in a Teaching and Learning Environment

Collaborative services

Related Approaches

More information

Some References

The digital lecture board is a novel , integrated teaching software. Basically it is an enhanced whiteboard tailored to the needs of synchronous teleteaching. Different media are integrated in an easy-to-use interface. The dlb provides flexibility for the use of media, support for collaborative group work and will be integrated in an overall teaching environment which will support most of the synchronous teleteaching requirements (construction, transmission, recording, retrieval, playback, and preparation of lectures and teaching materials). Currently we are using the MBone video conferencing tools (vic, vat, and wb) for remote lecturing. The experiences we gathered with these tools indicate that they are not sufficient for the purpose of teleteaching, because they are not powerful enough to support team work. They are also not flexible enough concerning the use of different media and they do not provide an integrated user interface while being somewhat difficult to handle and to set up by non-experts. Moreover, they do not allow synchronized recording of lectures (together with wb).

The following screenshot shows version 1.6a11 of the dlb with a sample slide. Clicking on the image brings up a larger version of the screenshot.

Reliable multicast/unicast data transmission

Usage of a variety of media formats: ps, gif, ppm, pcx, bmp, eps, ascii

Graphical objects: rectangles, ovals, lines, arrows, polylines, polygons

Editable text objects

Extended editing functions for graphical objects and text

Joint editing (source synchronized)

Clipboard feature: Cut, Copy, Paste, Delete, Group, Ungroup, and Undo

Zooming 

On-line and off-line mode (for the preparation of lectures or sessions)

Annotation mode

SGML-like document format for dlb documents

Configurable, easy-to-operate user interface

Collaborative services such as telepointers, voting, online-feedback, and attention 

Late Join

Synchronized recording and playback of sessions with the VCR on-demand service [Hol97]

RTP/RTCP standard conform

Network compatible to the AOF whiteboard (University of Freiburg)

Private sessions through encryption

 

 
 
 

Upcoming features:

Integration of vic and vat in the user interface

build-in animations

WWW dlb document viewer

Support of distance group work

Interface to a multimedia database which holds teaching and learning materials

Foor control and session control for tightly-coupled sessions

...

The handling of media objects is basically different to other standard whiteboards such as wb where one has only a single background slide (ps). Drawing operations are performed over this background slide. The dlb is more flexible concerning the use of media objects since it offers a plain, transparent drawing area where arbitrary media objects can be inserted. It is, for instance, possible to import several ps slides, which are also media objects, onto a single page. Actually, the software interface to the drawing area (tcl/tk canvas) allows to implement arbitrary media objects to be imported, e.g. digital video and audio.

We are currently working on  version 1.8, which is available for Solaris 2.6 (2.6.1), Irix 6.2 and Linux 2.0.35.  Basically, it is possible to port the dlb to Windows95 because its written in Tcl/Tk and C++. For displaying postscript pages, ghostscript is required. Tcl/Tk, C++ and ghostscript are available on most platforms.

Scaleable and efficient transmission of data to a group of participants is only possible using multicast. Since we rely on the Internet for remote lecturing, we need to employ the Multicast Backbone (MBone) for multicast data distribution. Basically, multicast IP is an unreliable, packet- oriented protocol. In contrast to audio and video data, lecturing material need to be transmitted reliably. At the beginning of our project, no commonly accepted reliable multicast protocol was available. Most of the protocols are either heavy-weight or they are integrated in applications (following the ALF concept, see SRM [Flo95]). So we decided to implement our own reliable multicast protocol SMP (scalable multicast protocol) which is based on SRM but extended with a local group concept. SMP runs as a separate process which can service multiple applications. It is configurable to a certain degree and supports data sharing, a generic late join mechanism, simple rate control and source ordering. SMP is already available in version 1.1b and can be used for other multicast applications also. [Gru97]

A dlb system comprises of several components as indicated in Figure 1. On the application level, the core part of the dlb embeds functional modules which are basically encapsulated C++ classes. The postscript module (ps), for instance, supports rendering of postscript pages by interfacing the ghostscript interpreter (gs). The telepointer module (tp) provides a distributed, shared pointing device. The img module allows for rendering most of the common image formats. The smp client is used to access the reliable multicast protocol smp. Moreover, we are using a security library (selib) for the secure data delivery. Modules can be used, for instance, to extend dlb's media capabilities with new media types (html, animations, etc.).

Fig. 1: Components of the dlb system architecture

 

Besides embedded modules, the dlb makes use of local services such as ghostscript (gs) for rendering postscript pages, the collaborative services model (csm) for managing collaborative services, and the scaleable multicast protocol (smp) for reliable multicast transmission. Remote services accessed via a network are, for instance, the Video Conference Recording on Demand service (VCRoD) or a multimedia database (MDB). Instead of integrating smp and csm  into the dlb core, we implemented them as separated service applications which can be accessed by a well-defined application programming interface. We favored this approach for the following reasons: first, other applications can also access csm and smp services and, second, the implementation of the dlb is eased since these two service tasks have been separated from the dlb. On the other hand, separate services increase system internal communication.

A teaching and learning environment consisting of a full-featured dlb along with a recording facility (e.g. the VCRoD service), a multimedia database for teaching materials, a WWW server, a VCRoD editing tool, and a WWW dlb document viewer would allow for several synchronous and asynchronous usage scenarios (see Fig. 2).

Fig. 2: Teaching and Learning Environment.

• Preparation/Pre-Authoring (asynchronous): Teachers and students use the dlb for the preparation of material for the synchronous teleteaching mode. They may access a multimedia database (MDB) or a local storage device (ls) for the retrieval of multimedia material needed for teaching and learning. The outcome of this mode is an off-line dlb-document which can be, for instance, a complete presentation for RLR, a small report of students for RIS, or a piece of group work for IHL. The dlb-document can be stored locally (ls) or on the multimedia database (MDB).
• Transmission/Teleteaching (synchronous): The prepared dlb-documents are used as a basis for synchronous teleteaching in the three different instructional setting RLR, RIS, and IHL. The material is transmitted to the whole class. Teachers and students can then employ the advanced synchronous features of the dlb such as, for instance, reference pointing (telepointer), forming sub-groups (session control), annotating (drawing tools), controlling the course of instruction (floor control), on-the-fly development and import of materials (drawing tools and access to ls or MDB), or discussions (audio and video). The result of this mode is on the one hand a modified dlb-document which can be stored by both teachers and students in order to save results. On the other hand, using the VCRoD service allows for the recording of the complete teleteaching session including all media streams (audio, video, telepointers, dlb actions, etc.).
• Revision/Post-Authoring (asynchronous): Based on the materials obtained from the transmission mode (dlb-document and VCRoD recording) , a complete multimedia document, enriched with further multimedia components (e.g. animations), can be produced by using the dlb, a VCRoD editor or further authoring tools. The multimedia document can be distributed off-line by CD-ROM or on-line via WWW. Obviously, the advantage of this approach for authoring is that production time is considerably reduced since material of mode 1 and 2 are basically a spin-off of synchronous teleteaching. In addition to the publishing issue, students may also use the modified dlb-documents of mode 2 in order to produce individualized, annotated lecture notes with the dlb, e.g. for the preparation of exams.

Retrieval (asynchronous): A light-weight WWW dlb viewer can be employed for retrieving lecture notes (dlb-document) from a WWW server for the purpose of viewing and printing. Moreover, the VCRoD service offers students, who missed the lecture or who want to review a certain difficult topic, the possibility to playback recorded lectures (VCRoD recording) as originally captured. The VCRoD service supports random access, fast-forward and rewind to arbitrary parts of the lecture [Hol97].

Today's teleteaching systems suffer a lack of communication channels compared to the traditional face-to-face instruction, since most systems support only audio, video, and joint editing of documents. Social protocols or rules control the human interaction and the course of instruction within a classroom. These mechanisms are difficult to reproduce in a remote situation and include, for instance, raising hands, giving rights to talk or to write on the blackboard, setting up work groups and reference pointing. Collaborative services provide mechanisms to support the communication of persons through computers in order to compensate as far as possible - by means of technology - the lack of communication channels in remote situations. The collaborative services model (csm) - developed for the dlb - implements enhanced floor control and session control mechanisms and policies. Floor control realizes concurrency control for interactive, synchronous cooperation between people by using the metaphor of a floor. A floor is basically a temporary permission to access and manipulate resources (e.g. a shared drawing area). Session control denotes the administration of multiple sessions with its participants and media. Session control increases social awareness in distributed work groups because members gain knowledge on each other and their status in the session. The csm keeps the collaboration state (the relationships between participants, floors, resources, and sessions) in a single object-oriented model. The model is replicated on each participant's workstation and held consistent by using an optimistic synchronization scheme. Applications using csm get either messages about the collaboration state or they can explicitly send queries to csm, e.g. to ask if the floor for drawing on the shared workspace is currently available. Just as smp, csm is implemented in a separate process which provides services to multiple applications. This is specifically useful if several application are involved in the same session. The csm supports the following features:

Administration of participants, groups, sub-groups, and super-groups,

management of resources and assignment to participants, groups, and sessions,

participants with different roles and privileges (e.g. teacher, student, etc.), and

different floor control policies (e.g. implicit control, explicit control, chair control, etc.).

For a more detailed description of the csm see [Hil97].

Besides various existing video conferencing systems such as NetMeeting, CUSeeMe, Intel's ProShare etc., which provide audio/video transmission, application sharing and standard whiteboard features, there are two approaches related to ours. The "Authoring on the Fly" (AOF) [Bac96] concept merges broadcasting of lectures with authoring of CBT software. In AOF lectures are transmitted with an extended whiteboard to a number of receivers. Interactivity is limited to the audio and video channel, modifications to the transmitted material are not possible for receivers. Thus, collaborative types of instruction are not supported. The sender's (teacher's) media streams are recorded locally. The synchronized recording together with lecturer slides and additional media, such as animations, are then transformed to a CBT course which can be either published on CD-ROM or accessed through the WWW. The Interactive Remote Instruction (IRI) system developed at Old Dominion University [Mal96] provides a very powerful, integrated teleteaching environment. The system can be used to view or make multimedia class presentations, to take notes in a multimedia notebook, and to interact via audio/video and shared tools. Furthermore, it provides class management and floor control. The system differs from ours in that IRI partly relies on analogue transmission of NTSC video signals and that collaboration is limited to application sharing.

Contact Jürgen Vogel via email (vogel@informatik.uni-mannheim.de) and/or check the publications about the dlb.

[Bac96] Bacher, C., Ottmann, T.: Tools and Services for Authoring on the Fly. In: Proceedings of ED-MEDIA'97, Boston 1996.

[Flo95] Floyd, S., Jacobson, V., McCanne, S., Liu, C., Zhang, L.: A Reliable Multicast Framework for Light-weight Sessions and Application Level Framing. IEEE/ACM Transactions on Networking, 1995.

[Gru97] Grumann, M.: Entwurf und Implementierung eines zuverlässigen Multicast-Protokolls zur Unterstützung sicherer Gruppenkommunikation in einer TeleTeaching-Umgebung. Master's Thesis (in German), Lehrstuhl Praktische Informatik IV, University of Mannheim 1997.

[Hil97] Hilt, V. & Geyer, W.: A Model for Collaborative Services in Distributed Learning Environments. In: Proceedings of IDMS'97, Darmstadt, LNCS 1309, 364 -375, 1997.

[Hol97] Holfelder, W.: Interactive Remote Recording and Playback of Multicast Videoconferences. In: Proceedings of IDMS'97, Darmstadt, LNCS 1309, 450-463, 1997.

[Mal96] Maly, K., Wild, C., Overstreet, C., Abdel-Wahab, H., Gupta, A., Youssef, A., Stoica, E., Talla, R.,Prabhu, A.: Virtual Classrooms and Interactive Remote Instruction. In: International Journal of Innovations in Education, 34(1), 44-51 1996.