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1.4 Synchronous Communication

Most remote education systems, including the introduced example, are pure asynchronous systems. However, asynchronous systems alone are not enough. They lack in terms of direct interaction and group work among participants, which are significant parts of education. As mentioned in section 1.3, synchronous communication tools are important elements of remote education systems. They can be used in several situations:

1.4.1 Examples of existing products

Two existing synchronous communication tools -- cTalk by Advanced Collaborative Solutions and WWWhiteboard by Link-Systems International are discussed in this section. Both products have been chosen because they allow sharing of images in virtual meetings. Important features of synchronous communication will be discussed later, as they relate to the introduced products. cTalk Design Review

The product cTalk Design Review1.2, marketed by ACS (Advanced Collaborative Solutions), allows real-time teleconferencing from remote locations. Its current version is 2.2, which can be downloaded freely. It runs only on PC's with Windows 9x and NT and requires Microsoft Internet Explorer and Microsoft NetMeeting to be installed.

cTalk is intended as a conferencing tool used by a team of remote participants to review CAD drawings. The initiator and host of a conference prepares a set of slides, where each slide can contain a single CAD drawing. The users are connected through a server, which relays each participant's actions to all other users as they occur. No dedicated server needs to be installed. Users are instead connected to special cTalk servers that are maintained by ACS. Before a user can host a review conference, he or she must sign up for a host account at ACS.

The supported file formats that can be loaded in a slide are BMP, DXF, DWG, SAT and PLT. The host can start the conference once the drawings that should be reviewed are loaded. Other conference participants can join the conference session from that time forward. Additionally, a telephone conference call through regular desktop telephones takes place in parallel.

The main area of every participant's cTalk application displays a single slide at a time (see figure 1.3). Only the conference host can switch to other slides and all other users follow automatically to the same slide. The contents of the shared slides can be saved by the users for later use.

Figure 1.3: The cTalk Client


The review of a slide is aided by markup tools accessible from the tool bar. Every participant can draw shapes or write text on top of the slide in his assigned color. A special tool is the interactive pointer. This tool allows participants to point to any place on a slide using their mouse. The pointer is represented by the user's assigned color and can be seen by the other users. More than one participant can use the pointer tool simultaneously at the same time.

In addition to slides, it is possible for the conference host to take all participants to a web site of his or her choice. The web page is displayed to the other participants like a regular slide. It is however not possible to make markups inside a displayed web site. The host, and only the host, can navigate through the web space and all participants will automatically follow the host to the same web page. WWWhiteboard

WWWhiteboard1.3 is an interactive graphical tool for live communication developed and marketed by Link-Systems International. This tool is a web-based application, where participants have access to a shared whiteboard, which is accessible through web browsers. The front ends of the white board are Java applets embedded in web pages. WWWhiteboard is therefore very system independent since Java enabled web browsers exist for almost every platform. The network communication among applets is tunneled through a central server. This server is however only available for SunOs, Solaris, Linux and NetBSD. A Windows NT version is planned but not available yet.

Every applet displays a single window, the white board, on which the user can set, move and remove several objects (see figure 1.4). The content of this window is shared between the participants. Supported objects are text strings, mathematical expressions, lines, circles, boxes and images. Immediately after a user places or paints an object on the shared screen, it is transferred to all connected applets. An object can also be moved or deleted. Those operations are however restricted to the creator of an object.

Figure 1.4: Two WWWhiteboard Applet Front-Ends participating in the same session.


The bottom part of the applet windows contains a chat area. All text entered here by a user is forwarded to the other users. Each text line is marked in a different color.

1.4.2 Comparison of the Introduced Products

WWWhiteboard is compact and it is possible to sketch simple problems very quickly. The users are however anonymous and it is therefore hard to follow a discussion in the chat area since the participants are distinguishable only by their color. In addition, there is the disadvantage that everything on the white board is lost as soon as the last participant leaves the session.

cTalk overcomes the flaws of WWWhiteboard, but it has the big disadvantage in that it is only usable on win32 platforms. Further, the participants can only communicate via the telephone conference. The system is therefore not very suitable for user groups that are dispersed over great distances. Expensive long distance telephone costs may be tolerable for companies but surely not for the private sector.

Even though the afore mentioned systems are different and are intended for different fields, there are certain factors that should be ensured by a synchronous communication tool:

next up previous contents
Next: 1.5 A Synchronous Distributed Up: 1. Basics and related Previous: 1.3 CSCW and Computer
Norbert Harrer