Subproject 4: HTML-WML Transcoding System Jia-Shung Wang Computer Science Department National Tsing Hua University March 27, 2001

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

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

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.

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

Demos of Transcoding Contents from enYES 鉅亨網 USAtoday CS, NTHU NTHU VOD

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 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 This is the first card... This is the second card. HTML Example page. This is a headline. This is a paragraph.

System Overview Web Server Multimedia Content CGI Scripts etc. Translation Server WML Generator Client WML Browser Etc. HTTP HTML Parser WAP HTML-WML Translator HTML, WML Documents HTTP

Features 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 Response

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

Components (cont’d) 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

Components (cont’d) 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

HTML to WML Conversion 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, …

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

Original Document

Tables to Lists

One Table One Deck

Preview First

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.

Evaluation of Searching After Translation Preview First One Table One Deck Tables to Lists GoodBestWorstUser Friendly S/2CS/2N/2 Average Deck Access Time

Performance Evaluation 5.4%57.2%16, %46.7%11, %22.0%7, ,7278,32521, ,7406,13717, ,3619,47124,359Experiment #1 Experiment #2 Experiment #3 HeadersText Source (bytes) Images (bytes) With Images Without Images ReductionHTML Pages WML Decks (bytes) 25.2%40.3%12,06217,96620,3639,568Experiment #4

Performance Evaluation (Experiment #1: What’s WAP ) Preview Deck 1 Deck 3.2 Deck 3.1 What’s WAP Preview Deck 3Deck 2Deck 1 WAP Forum

Performance Evaluation (Experiment #2: NTHU Web Page) Preview NTHU Preview Deck 1 Preview Deck 1Deck 2.1 Deck 2.2 Current Status Preview Deck 1Deck 2.1 Deck 2.2 History Deck 3.1 Deck 3.2 About NTHU

Performance Evaluation (Experiment #3, NTHU CS Web Page) Preview Deck 1 Deck 3.2 Deck 3.1 Faculty Preview Deck 1 NTHU CS Deck 3.4 Deck 3.3 Deck 3.6 Deck 3.5

Performance Evaluation (Experiment #4, IETF Web Page) Preview Deck 1 IETF Preview Deck 1Deck 2.1 Deck 2.2 Internet-Drafts Preview Deck 1 Deck 2.2 Deck 2.1 Internet-Drafts Index Deck 2.4 Deck 2.3Deck 2.5 Preview Deck 1 Deck 2.2 Deck 2.1 DNSOP Deck 2.4 Deck 2.3Deck 2.5

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

Summary Design an HTML to WML transcoding system with 1.Analyzing and filtering HTML contents 2.Image/icon resizing 3.WML browsing mode design and WML conversion tool 4.compression and decompression modules of the WML data. 5.WML transmission control