Desarrollo de una arquitectura software para aplicaciones de educaci

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First International Workshop on Multimedia
Interactive Protocols and Systems
MIPS 2003 November 18-21, 2003 Napoli (Italy)
A Mixed XML-JavaBeans Approach to Developing
t-Learning Applications for the Multimedia Home
Platform
Martín López Nores Department of Telematic
Engineering University of Vigo (Spain)
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Organization

• Introduction to t-learning.
• The MHP standard.
• Solutions for broadcast services.
• Implementation details.
• Summary and future work.

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A Few Words about t-Learning
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Introduction

• A lot of work is being done on distance learning.
• In order to overcome the limitations of
  traditional learning.
• Access to education is considered key to maintain
  a regions competitiveness.

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Introduction

• Several major technological approaches have been
  defined.
• The future points towards convergence.
• Obstacles networks, interoperability and users.
• Currently, the different mediums demand different
  solutions.

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t-Learnings Advantages...

• There is at least one TV in nearly 100 of
  households in developed countries.
• Internet not expected to go beyond 70.
• Television is easy to use for everybody.
• IDTV helps to prevent social exclusion in the
  access to education.
• Overcomes economical and cultural barriers.
• No need to buy a computer.
• No need of technological knowledge.

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... and Peculiarities

• A set-top box is not a computer.
• Lower computing power.
• Limited user interaction capabilities.
• A TV screen has low resolution.
• Simple user interfaces with big visual elements.
• IDTV is a natural medium for broadcast and
  handling multimedia content.
• Users are predominantly passive.
• TV is considered as a medium for entertainment.
• IDTV is ideal for informal learning
  (edutainment).

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Strategies for Interactivity
User-driven

• Applications respond to the users actions.
• Typical in e-learning services.

Media-driven

• The evolution of pieces of media guides users and
  controls the flow of applications.
• Main option for t-learning.

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The MHP Standard
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The Multimedia Home Platform

• Published by the DVB (Digital Video Broadcasting)
  Consortium in February, 2000.
• It defines a neutral framework for IDTV
  applications and services.
• Increasingly popular among broadcasters and
  relevant enterprises.
• Initially European ones.
• The recent GEM (Globally Executable MHP)
  specification prepares the way into the USA and
  Japan.

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Communication Issues

• Communication in IDTV is highly assymetric.
• Broadcast networks and (optional) return
  channels.
• The MHP framework
• MPEG-2 transport streams for broadcasting live
  audio and video, and DSM-CC object carrousels for
  other resources.
• TCP/IP and service-specific protocols for the
  return channel.
• The availability of a return channel determines
  the interactive capabilities.
• Simulated and real interactivity.

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The Object Carrousel

• Main mechanism to broadcast data in MHP.
• A group of files transmitted in a cyclical way.
• A read-only filesystem over an MPEG-2 transport
  stream.
• Resources are not always available immediately
  when needed.
• There may be noticeable latencies.

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The Problem of Latencies

• Latencies can be extremely annoying.
• Example
• 520 KB _at_ 256 Kbps 16 seconds per cycle !
• Nobody would wait so long for a program to start.
• MHP offers several ways to control latencies
• Caching, preloading and asynchronous loading of
  contents.
• Other contributions
• Adequate planning of the carrousels.
• Careful construction of the applications.

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The MHP Profiles

• MHP defines several receiver profiles.
• Features and cost tailored to the services
  required.
• We pay special attention to broadcast services.
• Inexpensive and fast to develop.
• Suitable for edutainment.
• Interactivity may drive users towards more active
  profiles in their use of TV.

Extensions for e-mail
and web browsing
Return channel for real
interactivity
Internet access
Interactive broadcast
Enhanced broadcast
Simulated interactivity
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Principles of the Architecture
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Structure of the Courses
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Conditional Access

• Units have a locked/unlocked state.
• Can be changed in response to any event.
• The composition of a course is summed up in a
  directed graph, defining
• The ordering of the units.
• The access dependencies.
• This information must be available at the
  receivers.
• Local take of decisions.

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Contextual Binding

• A simple and effective solution for the
  synchronization of multiple sources of
  information.
• Including the broadcast streams (media-driven
  units).
• It is based on contexts.
• Identifiers linked to pieces of information.
• Defined differently for the different types of
  content.
• Timestamps in fragments of audio and video.
• Regions in images.
• Anchors in a text.
• Options in menus, etc.

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Templates (I)

• Templates are a common feature in many
  development tools.
• Make development tasks faster.
• Enhance software reuse.
• Help to separate content from graphical
  appearance.
• Their use in IDTV applications offers additional
  advantages.

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Templates (II)

• Templates are configured during runtime.
• Not at design time.
• The cost of runtime configuration is masked by
  latencies and loading times.

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Templates (III)

• The object carrousel transports
• the Java class file of the template,
• much smaller XML configuration files.
• Advantages
• More files can be kept in the cache.
• Higher efficiency.
• The size of the carrousel decreases.
• Lower round-trip time?? lower latencies.

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ImplementationDetails
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Design Goals

• No need of programming knowledge.
• Flexibility and support for all the phases of
  development.
• Based on free, open technologies.
• Low cost.
• Extensibility.
• Interoperability.

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Types of Applications
DVB-J

• Applications programmed in Java.
• Two main restrictions
• MHP APIs.
• Xlet lifecycle.

DVB-HTML

• A declarative language, based on Internet
  standards.
• XHTML, CSS, cookies, etc.

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Foundational Technologies XML

• A standard syntax for
• the composition of the courses,
• the configuration files for a template,
• the definition of contexts in the different types
  of information.
• Also used when assembling pedagogical units.
• To communicate with content-management systems.
• SCORM, IMS, etc.

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Foundational Technologies JavaBeans

• A components architecture for Java.
• Promotes components reuse.
• Provides for visual development.
• Beans are building blocks to construct
  applications.
• Interrelations handled by means of event
  adapters.
• Enough for simulated interactivity.
• Not for non-broadcast services.

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A CASE Tool for t-Learning

• We have implemented our approach on top of the
  NetBeans Platform.
• Features
• Entirely visual development.
• Simple assembling of pedagogical units.
• By retrieving content from repositories or
  creating it ad-hoc.
• Several wizards and assistant tools.
• To define the composition of the courses.
• For the automatic creation of multiple-choice
  tests.
• To delimit contexts in the different types of
  information.
• Automatic generation of the transport streams.

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Summary and Future Work
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Main Conclusions

• Human and technical factors advice against direct
  translation of e-learning solutions.
• Broadcast services are essential at an initial
  stage.
• Preparing the way towards highly-interactive
  services.
• The MHP standard provides a satisfactory
  platform.
• Simulated interactivity.
• Latencies.
• Predominance of multimedia contents.
• Essential distinction between user-driven and
  media-driven strategies.

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Future Work

• Exploit the power of the return channel.
• Real interactivity with applications and other
  users.
• Personalization of contents.
• Creation of virtual learning communities,
  involving people with shared interests.
• Analyze new multimedia formats MPEG-4.

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End