Subproject 4: HTML-WML Transcoding System

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Subproject 4 HTML-WML Transcoding System

• Jia-Shung Wang
• Computer Science Department
• National Tsing Hua University
• March 27, 2001

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Outline

• Motivation and Issues
• Examples of Transcoding
• System Overview and Translation Flow
• Some HTML to WML Conversion Strategies

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Information Appliances

• Different design constraints based on intended
  use, enhances ease of use
• Desktop PC
• Mobile PC
• Desktop Smart Phone
• Mobile Telephone
• Personal Digital Assistant
• Set-top Box
• Digital VCR
• Implications
• Shift from computer design to consumer design
• Heterogeneous standards, hybrid networking
• Interactive networking, access on demand, QoS

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Motivation

• Rapidly growing diversity of wireless
  communication devices
• The incredible growing of the amount of available
  HTML web pages on the Internet
• Solutions for mobile devices with WML browsers to
  access the existing HTML or WML pages on the
  Internet.

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Issues

• Device-enabled service for WML mobile devices
  with different types of screen
• Bandwidth-driven transmission for rapid response
  and fast delivery speed
• The usage of browsing behavior
• The resizing of images /icons
• The compression of the resulting WML data

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Demos of Transcoding

• Contents from
• enYES ???
• USAtoday
• CS, NTHU
• NTHU
• VOD

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Discussions

• enYES provides two versions regular HTML and WAP
  to serve PC users and mobile device users
  separately.
• USAtoday also provides content (simplified
  version) for users with Palm.
• NTHU, CS-NTHU homepagesIf we keep the original
  figure for saving the link information, then the
  page layout becomes old. (using HTML browser
  withBrowse-It).
• VOD homepage, one-column text no significant
  difference after transcoding.

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Usage of Browsing Behavior

• The automatic translation seems complicated
  because of the diversity of content posted on an
  HTML page.
• It is unlikely to have a universal conversion
  strategy to translate every HTML page to
  sequences of WML decks effectively.
• However, it seems a good idea to categorize the
  browsing behavior to classify the HTML page to be
  translated first.

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Usage of Browsing Behavior (contd)

• After doing that we may realize what the client
  requires. Then we can have a corresponding
  conversion to extract the acquired content
  step-by-step and translate them into some
  predictable and small sized WML documents.
• We believe that there would be some adequate
  conversions for some kinds of web pages after
  classification.

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Related Works Transcoding Proxy of IBM alphaWorks

• It has a goal to manager different version of
  contents with different fidelities and modalities
  in order to adapt the delivery to different
  client device.

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Related Works Intel Quick Web Technology

• New software capability that helps Internet
  providers and digital distribution companies
  increase the delivery speed of Web pages
  containing photos, drawings and other graphics.
• It uses two key techniques, Compresses and
  Caches.

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Related WorksSpyglass Prism

• Spyglass Prism dynamically adapts Web content to
  match various non-PC devices.
• It functions as a proxy server, caches the
  converted content, and dynamically converting
  standard HTML to WML.

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Related WorksProxy Architecture for Efficient
Web Browsing over Cellular Networks

• Decreases the access time of browsing WWW in
  narrow-band wireless environment.
• It adopts persistent connection and pipelining
  technique based on proxy architecture to improve
  the HTTP process between the client and the proxy
  server.

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Comparisons betweenHTML and WML

• Both make use of tags and attributes.
• Similar character set, syntax and data types.
• Two special elements of WML structure
• Deck and Card
• Different design goal
• HTML To Publish hypertext on the World Wide Web
• WML For narrow network bandwidth devices with
  small displays, limited memory and fewer
  computational resources.

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Examples of HTML and WML
WML ltwmlgt ltdeckgt ltcardgt
ltpgt ltdo type"accept"gt
ltgo href"card2"/gt
lt/dogt This is the first card...
lt/pgt lt/cardgt ltcard id"card2"gt
ltpgt This is the second card.
lt/pgt lt/cardgt lt/deckgt lt/wmlgt
HTML lthtmlgt ltheadgt lttitlegt
Example page. lt/titlegt lt/headgt
ltbodygt lth1gt This is a
headline. lt/h1gt ltpgt
This is a paragraph. lt/pgt
lt/bodygt lt/html gt
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System Overview
Web Server
Translation Server
HTML, WML Documents
HTML Parser
WAP
WML
HTTP
HTML-WML Translator
WML Browser
HTTP
Multimedia Content
WML Generator
Etc.
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Features

• An HTML-WML Translator on the Translation Server
• Both HTTP and WAP requests are acceptable.
• Java Servlet API compatible
• Server- and platform-independent

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Translation Server Components and Flow
Network Protocol
Proxy
Request
Request
Response
Response
HTML Parser
WML Generator
Link Builder
Filter
Document Analyzer
Decks Cards
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Components

• Gateway
• Accept requests from clients
• Return appropriate responses
• Proxy Servlet
• Get the requested remote documents
• Determine to pass or convert
• Cache the converted results

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Components (contd)

• HTML Parser
• Parse the HTML document as a parse tree
• Document Analyzer
• Analyze the parse tree
• Filter
• Filter any objects unnecessary or not supported
  by the client device
• Image/icon resizing

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Components (contd)

• Content Divider
• Split a document into multiple, small-size
  documents
• Link Maker
• Insert extra links to make small documents reach
  one another
• WML Generator
• Produce well-formed WML documents and return them
  to Proxy Servlet

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HTML to WMLConversion Tools

• Semi-automatic
• Used for rich HTML documents
• The conversion form is designated manually with
  the help of analysis and editing tools.
• The resulting forms are distributed to the
  gateway servers.
• Automatic
• Used for simple documents, such as News and BBS,
  

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HTML to WMLConversion Strategies

• Strategy I Tables to Lists
• Simply removing all layout elements such as table
• Let all the contents arrange into only one column
  with a fixed width
• Strategy II One Table One Deck
• Extracting each table to form a deck

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HTML to WMLConversion Strategies (contd)

• Strategy III Preview First
• a. One Table One Deck
• b. Collect all the first card of every deck as
  preview cards
• c. Arrange these preview cards to form an preview
  deck, which will be transmitted first, every
  preview card will have a link to its
  corresponding deck

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Original Document
ltcontent 1_1gt
lttablegt
ltsection 1gt
ltcontent 1_2gt
ltcontent 2_1gt
ltcontent 2_2gt
ltsection 2gt
ltcontent 2_3gt
ltcontent 2_4gt
ltcontent 2_5gt
ltdocumentgt
lttablegt
ltcontent 3_1gt
ltcontent 3_2gt
ltcontent 3_3gt
lttablegt
lt section 3gt
ltcontent 3_4gt
ltcontent 3_5gt
ltcontent 3_6gt
lt section 4gt
ltcontent 4_1gt
ltcontent 3_7gt
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Tables to Lists
ltcontent 1_1gt
ltcontent 1_2gt
ltcontent 2_1gt
ltdeckgt
ltcontent 2_2gt
ltcontent 2_3gt
ltcontent 2_4gt
ltcontent 2_5gt
ltdocumentgt
ltdeckgt
ltcontent 3_1gt
ltcontent 3_2gt
ltcontent 3_3gt
ltcontent 3_4gt
ltcontent 3_5gt
ltdeckgt
ltcontent 3_6gt
ltcontent 3_7gt
ltcontent 4_1gt
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One Table One Deck
ltcontent 1_1gt
ltdeckgt
ltcontent 1_2gt
ltcontent 2_1gt
ltcontent 2_2gt
ltcontent 2_3gt
ltdeckgt
ltcontent 2_4gt
ltcontent 2_5gt
ltdocumentgt
ltcontent 3_1gt
ltcontent 3_2gt
ltdeckgt
ltcontent 3_3gt
ltcontent 3_4gt
ltcontent 3_5gt
ltcontent 3_6gt
ltdeckgt
ltcontent 3_7gt
ltcontent 4_1gt
ltdeckgt
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Preview First
ltcontent 1_2gt
ltdeckgt
ltcontent 2_2gt
ltcontent 1_1gt
ltcontent 2_3gt
ltcontent 2_1gt
ltdeckgt
ltdocumentgt
ltcontent 2_4gt
ltdeckgt
ltcontent 3_1gt
ltcontent 2_5gt
ltcontent 4_1gt
ltcontent 3_2gt
ltcontent 3_3gt
ltdeckgt
ltcontent 3_4gt
ltcontent 3_5gt
ltcontent 3_6gt
ltdeckgt
ltcontent 3_7gt
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Strategy Evaluation

• Assuming we have S sections in a document and the
  document is translated to N WML cards.
• Every deck contains at most C cards.
• Assuming that the contents in the same tables are
  similar.

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Evaluation of Searching After Translation
Preview First
One Table One Deck
Tables to Lists
Good
Best
Worst
User Friendly
S/2C
S/2
N/2
Average Deck Access Time
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Performance Evaluation
Reduction
HTML Pages
WML Decks (bytes)
Source (bytes)
Images (bytes)
With Images
Without Images
Headers
Text
3.5
22.0
7,440
176,361
9,471
24,359
Experiment 1
7.4
46.7
11,232
126,740
6,137
17,937
Experiment 2
5.4
57.2
16,891
280,727
8,325
21,203
Experiment 3
25.2
40.3
12,062
17,966
20,363
9,568
Experiment 4
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Performance Evaluation (Experiment 1 Whats WAP)
Whats WAP
WAP Forum
Preview
Preview
Deck 1
Deck 3.1
Deck 3
Deck 2
Deck 1
Deck 3.2
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Performance Evaluation (Experiment 2 NTHU Web
Page)
Current Status
History
NTHU
Preview
Preview
Preview
About NTHU
Deck 1
Deck 2.1
Deck 1
Deck 2.1
Deck 3.1
Preview
Deck 1
Deck 2.2
Deck 2.2
Deck 3.2
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Performance Evaluation (Experiment 3, NTHU CS
Web Page)
NTHU CS
Faculty
Preview
Preview
Deck 1
Deck 3.1
Deck 3.3
Deck 3.5
Deck 1
Deck 3.2
Deck 3.4
Deck 3.6
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Performance Evaluation (Experiment 4, IETF Web
Page)
IETF
Internet-Drafts
Internet-Drafts Index
DNSOP
Preview
Preview
Preview
Preview
Deck 2.1
Deck 1
Deck 1
Deck 2.1
Deck 2.1
Deck 1
Deck 1
Deck 2.2
Deck 2.2
Deck 2.4
Deck 2.2
Deck 2.4
Deck 2.3
Deck 2.5
Deck 2.3
Deck 2.5
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Implementation

• Goal Portability, reusability, and crash
  protection.
• Translation server under Java environment with
  Java Servlet, Java HTML Tidy, and XML Parser for
  Java.
• Servlet-enable server Avenida Web Server and
  Nokia WAP Server
• Microsoft Windows NT Workstation 4.0 with Service
  Pack 5

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Summary

• Design an HTML to WML transcoding system with
• Analyzing and filtering HTML contents
• Image/icon resizing
• WML browsing mode design and WML conversion tool
• compression and decompression modules of the WML
  data.
• WML transmission control