Multimedia Architecture Offering Open Distance Learning Services over
`Internet.
`
`A. Bazaios1, C. Bouras1,2, P. Lampsas1,2, P.Spirakis1,2, P. Zarafidis1, A. Zoura1
`
`1. Computer Engineering and Informatics Department, School of Engineering, University of Patras,
`GR-26500, Patras, Greece. Tel +30 61 996182, e-mail: {bazaios, zarafidi, zoura}@ceid.upatras.gr
`
`2. Computer Technology Institute, Kolokotroni 3, GR-26221, Patras, Greece. Tel. +30 61 994318, e-
`mail {bouras, lampsas, spirakis}@cti.gr
`
`ABSTRACT
`
`The increase in the use of the Internet not only as a
`repository of resources for learning but also as a
`means for the delivery of courses and specially
`prepared
`teaching material
`is a particularly
`significant innovation in the range of education.
`The main concept here is a Virtual class, which is
`based on the principles of CSCL (Computer
`Supported Collaborative Learning) systems. This
`paper describes an
`integrated, WWW based
`platform for the development of web enabled
`environments over TCP/IP networks, such as
`Internet. This platform is designated through a
`Teletraining
`and
`Collaborative
`Learning
`Application. The proposed platform aspires to be
`an efficient solution for a group of students and
`teachers that need a shared workspace, supporting
`remote interactive lectures, flexible exchange of
`teaching material and various communication
`utilities, with focus on transparent and secure
`interaction.
`
`I. INTRODUCTION
`for
`telematics
`applications
`Multimedia
`communication and co-operative learning provide
`tutor and trainees with the ability of continual,
`close and efficient Cupertino, without
`the
`limitation of physical presence in a common place.
`As the WWW (World Wide Web) is a standard for
`distributing multimedia/hypermedia information, a
`distance learning service should be based on the
`WWW and encompass all the kinds of media that
`would make it attractive and really useful, such as
`text, images, audio, and video.
`Well known tools implementing various features
`needed by an environment for collaboration and
`distant
`learning
`are Microsoft Netmeeting,
`Netscape Conference, RecPhone, etc. However, the
`tools mentioned above do not sufficiently combine
`the centralized control, the broad use over any
`
`operating system and the simplified access to the
`application through a web browser. Moreover, one
`of the greatest problems of an interactive learning
`and working environment among remote users is
`the vast amount of information that has to be
`exchanged in order to ensure an unambiguous
`interaction.
`What has been mentioned above has inspired our
`research efforts and motivated the presentation of a
`flexible solution to the restrictions posed above,
`based on the use of a collection of network
`technologies. The resulting architecture supports a
`training group and provides it with an application
`just through a web browser and a permanent or
`dial-up Internet connection with the Web server,
`without any additional installation in the local
`station. CGI, Java and Javascript are used
`to
`overcome the disadvantages of the passive features of
`HTTP protocol and provide the means for a relatively
`easy and quick enrichment of the interface and the
`services developed upon this platform. The basic
`media such as text and images can be transferred
`via the HTTP protocol while the continuous media
`are handled using MBONE architectures. The
`reasons for this separation stem from the weakness
`of HTTP protocol to accommodate media with real
`time characteristics, such as audio and video.
`This architecture supports a live workspace, in the
`context of a lesson. The lesson supports remote
`interactive lectures, remote instructor observation
`and immediate correction of students’ work. The
`same workspace provides file exchange and
`annotation during
`the course, as well as
`collaboration between students, via off-line and on-
`line
`communication
`and
`e-mail
`service.
`Furthermore,
`the
`teacher
`is provided with
`additional attributes, so as
`to facilitate
`the
`procedure of
`remote
`tutoring and distance
`education.
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`the
`
`following
`
`files
`
`in a
`
`II. FUNCTIONALITIES OF THE
`APPLICATION
`In order to create a complete distance education
`system which will satisfy the needs of a learning
`group, the application is designed as an emulation
`of a class environment. So, the concept of the
`virtual class arises, rendering it a telematics tool
`which
`realises Open and Distance Learning
`environments.
`The application will provide
`functionalities/features:
`♦ Ability
`to
`retrieve and edit
`hypermedia environment.
`♦ Send and receive electronic mail messages in
`an integrated environment.
`♦ Ease of use of hypermedia systems, provision
`of effective navigation tools. This feature is
`supported by the Web browser used to access
`the application.
`♦ Maximization of the amount of educational
`material covered, minimization of the amount
`of
`time
`spent
`learning
`the material,
`maximization of the students’ retention of the
`material. This is achieved by combination and
`exploitation of all document types in order to
`convey the material more successfully.
`♦ Provision of students with as much control as
`possible over when and how they learn the
`instructional material. Also, storage of the full
`lecture including explanations and annotations
`given during the lecture time, will be provided.
`That’s to say that students not only attend the
`lesson on-line but can access it any time later
`(off-line) as well as their notes on it, achieving
`flexible reuse and adaptation of the existing
`material.
`♦ The teacher is able to broadcast information
`(lectures, examples, solutions) and multimedia
`courseware, to every participating student.
`♦ Participants will be able to share applications.
`In other words, direct interaction of the teacher
`on the student’s computer for interactive work.
`♦ A whiteboard with which the teacher can
`broadcast a
`selected
`screen
`information
`(including a pointing device)
`♦ Support
`of
`collaborative
`courseware by several authors.
`♦ Bi-directional and multi-directional (multicast)
`independent communication between teacher
`
`authoring
`
`of
`
`and students for message exchange and real
`time audio and video conversation.
`♦ Support for note-taking capabilities in order to
`help students effectively organize the content
`of a courseware.
`♦ The teacher of course will be provided with
`additional
`features
`such
`as monitoring
`capabilities
`(of
`the participation of
`the
`students), assigning permissions, configuring
`the workspace according to the lesson’s needs
`etc.
`♦ For the effective tutoring it is desirable to
`restrict
`the
`information accessible by
`the
`student, in order not to “get lost” in irrelevant
`with the subject of the course information.
`
`III. PROPOSED ARCHITECTURE
`The overall architecture is based on the Client-
`Server model. The Server (Virtual Class Server )
`resides in the Virtual Class which consists of a
`powerful computer with a Web server and the
`server part of the application. The Virtual Class
`server will be able to operate using the MBONE
`technology and protocols for exchanging data
`formats (audio, video, chat, and White Board) and
`as storage space (WWW server capabilities) for the
`material of the lessons, where the user (trainer or
`trainee) has access, with a Web Browser, all the
`time.
`The Virtual Class Server is responsible for the
`communication between the trainer and the trainees
`during the On-Line part of the lesson. The main
`idea of the proposed architecture is to set-up a
`single Virtual Class Server per Virtual Class. The
`Server would be capable of taking over multiple
`lectures. Furthermore, the interaction between the
`trainer and the trainees is performed by the Server,
`which implements the commands of the users.
`The basic idea of the application’s environment is
`the lesson. A lesson includes the participants
`(students and experts), as well as files of any
`format (e.g. txt, doc, gif, etc.) manipulated by them
`and the On-Line part of the lesson which is
`conducted in predefined time.
`The Client of the application is obviously a Java
`compatible web browser that, along with the
`standard capabilities, supports frames and the RFC
`specification for the “File” type. The html pages
`and the Java applets of the application, as well as
`the lesson related files uploaded by the users, are
`stored in the Web Server. However, due to the need
`of extra information and statistics for the lessons
`and the files included, and the necessity of
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`definition of privileges and permissions of users on
`the lessons’ files, various control files have to be
`kept in the Virtual Class, where the application is
`installed.
`The major advantages of the proposed architecture
`are:
`♦ Interactive communication between users over
`the Internet, including audio, video and data
`exchange.
`the
`that
`sense
`the
`in
`♦ Modular design
`application specific network protocols are
`exclusively responsible for
`the
`interaction
`between the Clients and the Server.
`♦ It is an open-environment application, since it
`was developed in Java and CGI, in order to
`work independently of platforms.
`and
`♦ Reduced
`costs
`of
`development
`administration and increased flexibility. This
`implies that a single Virtual Class Centre is
`capable of taking over multiple lectures given
`by different
`trainers. Thus,
`the effective
`operation of the application requires the set-up
`of a single Virtual Class Server per Virtual
`Class.
`A very significant characteristic of the application
`is
`the selection of JAVA and CGI as
`the
`programming language. During the design phase, it
`was considered crucial
`the demand for full
`portability of
`the application. That
`is,
`the
`application should be able
`to be executed
`independently of the workstation of the user.
`
`It should be able to work either under Windows 95
`or a UNIX System or a Macintosh.
`At the same time it should have the ability to use
`the Internet
`infrastructure for reaching every
`potential user. In order to achieve what was
`mentioned above and to build a very easy-to-use
`tool, JAVA and CGI were selected.
`As a result of the above, the Virtual Class Server
`was implemented as a JAVA application and all the
`functions
`that support
`the Off-Line
`lesson’s
`procedure were implemented with CGI scripts.
`Protocols and languages used for the Server and the
`Clients are presented analytically in the following
`section.
`♦ Off-Line communication procedure:
`− The HTTP protocol was used over a TCP/IP
`network (Internet) in order for the trainees to
`communicate with the trainer and the Server. The
`HTTP
`protocol
`offers
`simplicity
`and
`standardisation.
`− The SMTP protocol was used to provide the
`E-Mail Service over a TCP/IP network.
`− The Perl language was used to create the CGI
`scripts offering compatibility and simplicity.
`− Finally Javascript, along with CGI scripts,
`were used to overcome the disadvantage of
`WWW passive protocol, HTTP.
`♦ On-Line communication procedure:
`− The TCP/IP protocol suite was used so that
`the trainees communicate with the trainer during
`the lecture.
`
`Trainee's Workstation
`
`Web Server
`(HTTP, CGI,
`JAVA)
`
`Dial up
`
`Teletraining
`Server
`(JAVA)
`
`Teletraining Center
`
`Trainee's Workstation
`
`Trainee's Workstation
`
`Network Infrastructure
`Internet TCP/IP
`(MBONE)
`
`Trainee's Workstation
`
`Trainer's Workstation
`
`Trainee's Workstation
`
`LAN
`
`Figure 1 The overall architecture of the Teletraining Tool.
`
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`− The Real-time Transport Protocol (RTP)
`delivers real-time traffic with timing information
`for reconstruction as well as feedback on
`reception quality. RTP works alongside TCP,
`providing end-to-end delivery of such data such
`as video-broadcasting and multi-participant
`interactive audio and video. The RTP protocol
`uses RTP Control Protocol (RTCP), to monitor
`the quality of service and to convey information
`about the participants in an on-going session.
`− The Real Time Streaming Protocol (RTSP),
`is an application level protocol for control over
`the delivery of data with real-time properties.
`RTSP provide mechanisms to: request delivery of
`real-time data; request a specific transport type
`and destination for the delivery of the data;
`request information about the data in a format-
`specific fashion; start, stop, pause the delivery of
`data; provide random access to various portions
`of the data (where applicable).
`the Internet
`− The MBONE structure of
`Network was used
`in order
`to avoid
`the
`congestion in the Virtual Class Centre. Using
`MBONE, the Virtual Class Server has to reflect
`the video and audio data only to one MBONE
`address in which all the users should listen. In
`this way it is avoided to open a unique channel
`with every potential user to transmit the rather
`large volume of data for video and audio.
`− The Gif, Jpeg formats were used for the
`compression of the slights that the trainer would
`demonstrate during the lecture in order to save
`bandwidth.
`− The H.323 or MPEG format handles the
`video compression and offers standardisation.
`− The T.120 protocol offers
`the needed
`standardisation for the data exchange part of the
`tool.
`− Finally, using the PCM protocol for audio
`compression, both quality and bandwidth saving
`are accomplished.
`The collaboration and learning environment of the
`CSCL application has been designed, so as to
`provide a great degree of flexibility, without
`causing navigational difficulties and cognitive
`overload for users. The workspace has been
`carefully divided into sections that interact with
`each other, avoiding distraction. Menus, hypertext
`links, buttons and text boxes prevent user from
`being confused and the on-line help makes the tool
`easy to use for everyone who has primitive
`experience in using a Web browser. The careful
`
`design of the user interface, together with guidance
`from the help section, in hypertext mode, make the
`tool fully operable for every learning goal.
`
`IV. CONCLUSIONS AND FUTURE
`WORK
`In conclusion, a software tool with the architecture
`described
`above
`and
`the
`aforementioned
`functionalities
`can
`emulate
`the
`learning
`environment of a classroom in a very effective and
`productive way. The WWW is the most convenient
`platform to accommodate the technology required
`for such a distance education tool.
`We will further investigate the new technologies,
`such as Corba or RSVP protocol, emerging from
`the rapid evolution of Internet, in order to adapt the
`tool to up-to-date advancements. Additionally, we
`closely follow
`the development of
`the Java
`platform, aiming to an integrated Java-enabled tool.
`
`V. REFERENCES
`[1] C. Bouras, D. Fotakis, V. Kapoulas, P.
`Lampsas, G. Papoutsopoulos, P. Spirakis, A.
`Tatakis. HIPPOCRATES: A multimedia tool
`for distance education, in: Proc. of ED-Media
`95, June 17-21 1995, Gratz, Austria, pp. 103-
`108.
`[2] C. Bouras, D. Fotakis, V. Kapoulas, S.
`Kontogiannis, K. Kyriakou, P. Lampsas, P.
`Spirakis, A. Tatakis. An
`Interactive
`Cooperative Teleworking Environment
`-
`Telemathea, in: Proc. of ED-TELECOM 96,
`June 17-22 1996, Boston, USA, pp. 37-42.
`[3] C. Bouras, V. Kapoulas, D. Miras, V.
`Ouzounis, P. Spirakis, A. Tatakis, “On-
`Demand Hypermedia/ Multimedia Service
`over Broadband Networks”, 5th International
`Symposium
`On
`High
`Performance
`Distributed Computing
`(HPDC-5),
`6-9
`August 1996, Syracuse, New York, USA, pp.
`224-231.
`[4] C. Bouras, V. Kapoulas, D. Miras, V.
`Ouzounis, P. Spirakis, “An Architecture for
`Interactive
`Distributed
`Multimedia
`Information
`Services”,
`International
`Conference on Telecommunications - ICT 97,
`Melbourne, Australia, 2-4 April, 1997.
`[5] Ming-Chih Lai, Bih-Horng Chen and Shyan-
`Ming Yuan. Towards a new educational
`environment, in: Proc 4th International World
`Wide Web Conf., World Wide Web J. 1
`(1995) pp. 221-230.
`
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`JAVA APPLETS
`
`Graphical User Interface
`HTML PAGES
`
`JAVASCRIPT
`
`Audio & Video
`
`Shared
`Applications
`
`JAVA
`
`Services
`File Transfer
`
`White Board
`
`Bulletin Board
`
`Privileged Access to
`Educational Materials
`Development Platform
`HTML
`
`CGI
`
`Chat
`
`E-Mail
`
`Audio & Video
`MPEG
`
`H323
`
`PCM
`
`Protocols & Standards
`Images
`GIF
`
`JPEG
`
`Collaboration
`
`T.120
`
`Communication
`
`RTSP
`RTP/RTCP RSVP
`
`HTTP
`
`TCP/UDP
`IP/IGMP
`
`Networks
`
`ISDN
`
`802.x
`
`ATM
`
`FDDI
`
`Figure 2 Protocol stack.
`
`[7] An Architecture for real-time communication
`systems’.
`IEEE
`Selected Areas
`In
`Communications, vol8, no3, Apr.1990.
`[8] Synchronization properties in a multimedia
`system,
`IEEE
`Selected
`Areas
`In
`Communications, vol8, no3, Apr.1990,
`pp.401-412.
`[9] Shepherd, D.Hutchinson, F.Garcia, G.
`Coulson Protocol support for multimedia
`applications. Computer Commun. vol.15, July
`1992, pp.359-366.
`[10] W. Richard Stevens. Unix Network
`Programming. Prentice Hall.
`
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