scorm-poster[1].doc
SCORM-compliant SMIL-enabled Multimedia Streaming
E-Learning System in Java EJB Environment
Sheng-Tun Li
Department of Information
Management National Kaohsiung
First University of Science and
Technology, Taiwan, R.O.C.
stli@ccms.nkfust.edu.tw
Chu-Hung Lin
Department of Information
Management National Kaohsiung
First University of Science and
Technology, Taiwan, R.O.C.
winf@ ai.nkfust.edu.tw
Huang-Chih Hsieh
Department of Information
Management National Kaohsiung
First University of Science and
Technology, Taiwan, R.O.C.
jack@ai.nkfust.edu.tw
ABSTRACT
The emergence of the SCORM specification has shed a light
toward standardization of e-learning which makes the reusability
and interoperability of learning resources feasible. However, the
existing SCORM-compliant asset model is over-simplified; only
few asset types are defined. On the other hand, W3C’s
declarative-style SMIL is becoming prevalent in designing Web-
based instructions with the consideration of temporality and
spatiality of the presentations. In addition, advances in real-time
multimedia technologies can further vitalize these instructions. In
this study, we propose a SMIL-enabled asset model with the
enhancement of multimedia streaming. To render SCORM-
compliant SMIL-enabled streaming contents, a Java applet-based
SMIL RTP/RTSP LMS system is designed in the Java EJB
environment to tackle the issue of platform interoperability. The
resulting system demonstrates an encouraging direction towards
more vivid and interactive SCORM-compliant e-learning.
Keywords
SCORM, e-learning, SMIL, multimedia streaming, EJB
1. INTRODUCTION
The rapidly increasing expansion of the Internet has brought
dramatic impact to one’s life and education alike. E-learning
differentiates from the traditional learning in its ability to train
anyone, anytime, and anywhere attributed to the openness of the
Internet. Without the temporal and spatial limitation, one can have
an independent and individual learning space. In general,
digitalized courseware is managed by the so-called Learning
Management System (LMS), which educates learners in the
courseware and keeps track of their learning behaviors. However,
most courseware in different LMS environments cannot be
interoperable directly, which impedes the attempt to share
learning resources. In addition, the heterogeneity existing in the
different LMSs is another impediment. It is inconvenient to
monitor and evaluate learner’s behavior from one environment to
another. All these hinder the sharing of learning resources
including LMSs and the contents. The emerging SCORM
(Shareable Content Object Reference Model) standard has been
developed to overcome these hurdles. The objective of the
specification is to facilitate the interoperability between SCORM-
compliant contents and SCORM-compliant LMSs, and to make
the valuable resources become durable, interoperable, accessible,
and reusable [1].
The present asset model of SCORM is over-simplified in
supporting multimedia presentations; vivid multimedia streaming
contents are usually excluded. In addition, designing the
SCORM-compliant streaming contents is not a trivial task.
Synchronized Multimedia Integration Language (SMIL) [2], built
on XML, proposed by W3C provides a simple way to design
multimedia presentations in a similar manner to HTML
documents. The SMIL specification meets three requirements of
multimedia document models, namely temporal, spatial and
interaction. To vitalize the asset contents of SCORM, this study
proposes a new asset model based on the SMIL and RTP/RTSP
standards so that the features of spatiality, temporality, interaction,
and streaming control can be added into assets. The extended
asset model conforms to SCORM, and thus any SMIL-enabled
asset can be imported to LMS and can communicate with LMS to
track the learners’ learning progress. Moreover, to facilitate the
interoperability of sharable course contents and LMS, we develop
a LMS on the top of Enterprise Java Bean (EJB), a distributed
component-based computing environment, for realizing SCORM-
compliant SMIL-enabled multimedia streaming contents.
2. SMIL-ENABLED MULTIMEDIA-
STREAMING ASSETS
In SCORM, the mechanism of Content Packaging is designed for
packing instruction contents and the navigation sequences. In a
content package, the portion of “organizations” specifies the
content structure and the browsed sequence of this content. The
“resources” session describes the instruction materials needed in
this content, such as the type and physical location of each
physical file. To create a SMIL-enabled asset, one may define an
unlaunchable asset, which refers to a physical filename ending
with “.smil” (see Table 1, for example).
Table 1. The unlaunchable SMIL-enabled asset
………
………
The intro.smil resource defines the rendering sequence of
text, image, and sound objects, RTP/RTSP streams synchronously
in different regions. Table 2 illustrates a porting of the resource.
3. SCORM-COMPLIANT LMS IN EJB
Figure 1 shows the system architecture of the LMS in the EJB
environment for realizing SMIL-enabled streaming assets.
Initially, the client has to download an API Adapter applet from
the Object Web Server. The applet is an EJB component
responsible for communicating with the LMS Server to access
learning resources. There are five enterprise Java beans in LMS
Server on the EJB container. UserEJB, an entity bean, is in
charge of confirming the legality of users and maintaining
information of the users. cListEJB, an entity bean, maintains the
list of instructions available in LMS so that students may choose
the courses they like to browse. ReadEJB, an entity bean, tracks
and records the learning behavior of each student in the data
model defined in SCORM’s RTE in the background. This bean
plays the most important role in the proposed LMS. C2SYSEJB,
a session bean, allows teachers or system adminstrators to import
courses or update course contents. In detail, this EJB object is
responsible for unzipping the content package (a PIF file) of
instructions, analyzing the imsmanifest, and allocating all physical
files in approciate locatons in a content repository. Moreover, this
session bean is the interface between EJB client and CourseEJB.
CourseEJB, an entity bean, endorses the C2SYSEJB bean to
access the content repository database. In the implementation, this
entity bean is wrapped by CourseEJB in a session bean therefore
one can access all the business functionalities without the
overhead of polling the entity bean.
Table 2. The content of SMIL resource: intro.smil
In order to support manipulating multimedia streams, SMIL
Parser parse SMIL-enabled assets and extract embedded
multimedia objects. If the extracted object is a RTP object, RTP
Handler will be invoked to receive RTP media streams,
synchronize audio and video srtream, and render them in the
client screen [3]. On the other hand, when client obtains a RTSP
object, RTSP Remote Controller is additionally called. Initially,
RTSP Server returns a SDP (Session Description Protocol)
message, which describes the information of RTP media to be
transmitted. After parsing the SDP data by SDP Parser, RTP
Handler receives and consumes the RTP stearms. During the
playback, RTSP Remote Controller handles the RTSP protocol
between client and RTSP Server. Besides, the client may issue the
Play, Pause, Fast Forward, Rewind, or Stop command to control
the streams.
RTSP Remote
Controller
RTP Handler
SMIL Parser
SDP Parser
API Adapter Applet
EJB Conainer
Course
C2SYSUser cListRead
Object Web Server
ObjectObject Object
RMI over IIOP
API Adapter
RTSP Server
RTP Server
Streaming media Server
Client
HTTP
SMIL Applet
RTSP
over TCP/IP
RTP
over UDP/IP
Local Content
Repository
Remote
Content
Repository
LMS Server
Figure 1. The proposed LMS architecture in EJB environment
4. EXPERIMENT
The proposed SMIL-enabled multimedia streaming e-learning
system has been experimented on the JBoss-3.0.3_Tomcat-4.1.12
EJB server [4]. Figure 2 illustrates the snapshot of browsing
SMIL-enabled RTP/RTSP multimedia assets with a VCR-like
control bar.
Figure 2. The presentation of SMIL-enabled RTP/RTSP asset
5. CONCLUSIONS
This paper proposed a SMIL-enabled asset model, which allows
W3C’s SMIL documents with multimedia streaming objects to be
embedded in instructions. We developed a Java applet-based
SMIL player and LMS for realizing and rendering such assets on
the learner’s Web browser. To handle the interoperability issue of
LMSs, the developed LMS was built in the Java EJB component-
based computing environment. With the SMIL-ability and the
streaming multimedia objects of assets, instruction contents could
be more vivid and interactive. The proposed asset model is
adherent to the SCORM standard; thus it can be sharable, reusable,
accessible and durable. The next research direction is to enhance
the proposed LMS by incorporating a directory service such as
LDAP (lightweight directory access protocol) so that the remote
SMIL-enabled assets can be interoperable and sharable.
6. ACKNOWLEDGMENTS
This work was partly supported by NSC91-2520-S-327-001,
Taiwan. The first author is supported in part by the Innovation
and Incubation Center at National Kaohsiung First University of
Science and Technology under contract 90B00025.
7. REFERENCES
[1] Sharable Content Object Reference Model Version 1.2,
http://www.adlnet.org/.
[2] “Synchronized Multimedia,”
http://wwww.w3.org/AudioVideo.
[3] Li, S.-T. and Chen, H.-C., “An Architecture-neutral
Approach to Web-based Synchronized Multimedia
Presentations with RTP Video Streams,” The Seventh
International Conference on Distributed Multimedia
Systems (DMS'2001), Tamkang University, Taipei,
Taiwan, September 26-28, 2001.
[4] Jboss, http://www.jboss.org.