Subproject 4: HTML-WML Transcoding System Jia-Shung Wang Computer Science Department National Tsing Hua University March 27, 2001
Motivation and Issues
Examples of Transcoding
System Overview and Translation Flow
Some HTML to WML Conversion Strategies
Different design constraints based on intended use, enhances ease of use
Desktop “Smart” Phone
Personal Digital Assistant
Shift from computer design to consumer design
Heterogeneous “standards,” hybrid networking
Interactive networking, access on demand, QoS
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.
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
Demos of Transcoding
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 homepages ： If we keep the original figure for saving the link information, then the page layout becomes old. (using HTML browser with:Browse-It).
VOD homepage, one-column text: no significant difference after transcoding.
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.
Usage of Browsing Behavior (cont’d)
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.
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.
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”.
Related Works Spyglass 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.
Related Works Proxy 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.
Comparisons between HTML 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.
Examples of HTML and WML WML <wml> <deck> <card> <p> <do type="accept"> <go href="#card2"/> </do> This is the first card... </p> </card> <card id="card2"> <p> This is the second card. </p> < /card > </deck> </wml> HTML <html> <head> <title> Example page. </title> </head> <body> <h1> This is a headline. </h1> <p> This is a paragraph. </p> </body> </html >
System Overview Web Server Multimedia Content Translation Server WML Generator WML WML Browser Etc. HTTP HTML Parser WAP HTML-WML Translator HTML, WML Documents HTTP CGI Scripts etc. Client
An HTML-WML Translator on the Translation Server
Both HTTP and WAP requests are acceptable.
Java Servlet API compatible
Server- and platform-independent
Translation Server: Components and Flow Network Protocol Proxy HTML Parser Filter Document Analyzer Decks & Cards WML Generator Link Builder Request Request Response Response
Accept requests from clients
Return appropriate responses
Get the requested remote documents
Determine to pass or convert
Cache the converted results
Parse the HTML document as a parse tree
Analyze the parse tree
Filter any objects unnecessary or not supported by the client device
Split a document into multiple, small-size documents
Insert extra links to make small documents reach one another
Produce well-formed WML documents and return them to Proxy Servlet
HTML to WML Conversion Tools
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.
Used for simple documents, such as News and BBS, …
HTML to WML Conversion 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
HTML to WML Conversion Strategies (cont’d)
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