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Structural Semantics for Accessibility and Device Independence
 

Structural Semantics for Accessibility and Device Independence

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Presentation describing the SADIe transcoding platform to the Information Management Group (IMG)

Presentation describing the SADIe transcoding platform to the Information Management Group (IMG)

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    Structural Semantics for Accessibility and Device Independence Structural Semantics for Accessibility and Device Independence Presentation Transcript

    • SADIe Structural-Semantics for Accessibility and Device Independence Darren Lunn
    • The Web…
      • The World’s largest repository of information
      • Designed with a focus on presenting information in a visual manner
        • Images
        • Animations
        • JavaScript
      • Some knowledge is only available implicitly from how the page looks
    • Implicit Knowledge = Advertisement = Banner = Main Content = Menu
    • Assistive Technologies
      • Visually impaired users use assistive technologies, e.g. Screen Readers
        • Render pages sequentially in audio
        • Achieved by accessing the underlying HTML code
      • But focus on visual presentation rather than content hampers this
        • Particularly if attention is not paid to coherent design
        • Tags and markup can be abused (e.g. using <h2> for large, bold, rather than headers)
        • Subtleties of visual presentation can be lost
    • CNN Example
    • Assistive Technologies
      • Traversal of content is in a serial “top-to-bottom”, “left-to-right” manner.
        • Based on the underlying HTML code.
      • Important information may not be encountered until later on.
      • Also, information such as menus or navigation may be repeated for every page on a site
        • This can prove tiresome if the user has to wait for the reader to read the menu each time a new page is visited.
      • Chunked pages and non-linear presentation further complicate matters
    • Existing Solution: Transcoding
      • A method of adapting and reformatting Web content so that it is suitable for a wide range of client devices
      • Heuristic Transcoding - Uses general rules and heuristics to find areas of the web page
      • Semantic Transcoding - Uses annotations to add metadata to the Web page in order to explicitly state the meaning of the elements
    • Heuristic Transcoding
      • Use general rules and heuristics to find areas of the web page
      • Once an area is found, then modify it in some way
      • Eg If (row at the top of table && Number of characters between <a> tags > Number of characters between <p> tags) then (Element is a page menu so do something)
    • Heuristic Transcoding <table cellspacing=&quot;0&quot; cellpadding=&quot;0&quot; border=&quot;0&quot; class=&quot;cnnCeilnav&quot;> <tr valign=&quot;middle&quot; height=&quot;22&quot; > <td><a href=&quot;/&quot;>Home</a></td> <td><a href=&quot;/WORLD/&quot;>World</a></td> <td><a href=&quot;/US/&quot;>U.S.</a></td> <td><a href=&quot;/WEATHER/&quot;>Weather</a></td> <td><a href=&quot;http://money.cnn.com/index.html&quot;>Business</a> . . . </tr> <ul> <li><a href=&quot;/&quot;>Home</a></li> <li><a href=&quot;/WORLD/&quot;>World</a></li> <li><a href=&quot;/US/&quot;>U.S.</a></li> <li><a href=&quot;/WEATHER/&quot;>Weather</a></li> <li><a href=&quot;http://money.cnn.com/index.html&quot;>Business</a></li> . . . </ul>
    • Heuristic Transcoding
      • General enough to be applied to a large number of web pages
        • All CNN pages follow this pattern, as do other pages that have a similar layout template
      • Can be inaccurate if the page is slightly different from the pre-existing rules
        • Eg CNN inserts an additional row containing advertisements
    • Semantic Transcoding
      • Uses annotations to add metadata to the Web page in order to explicitly state the meaning of the elements
      • Eg
      <menu> <table cellspacing=&quot;0&quot; cellpadding=&quot;0&quot; border=&quot;0&quot; class=&quot;cnnCeilnav&quot;> <tr valign=&quot;middle&quot; height=&quot;22&quot; > <td><a href=&quot;/&quot;>Home</a></td> <td><a href=&quot;/WORLD/&quot;>World</a></td> <td><a href=&quot;/US/&quot;>U.S.</a></td> <td><a href=&quot;/WEATHER/&quot;>Weather</a></td> <td><a href=&quot;http://money.cnn.com/index.html&quot;>Business</a> . . . </tr> </menu>
    • Semantic Transcoding
      • Very accurate
        • We can modify the page layout but as long as the annotations remain, the transcoding will work.
      • Every Web page must be annotated limiting the number of pages that can be transcoded
        • Time consuming
        • Issues of document ownership
    • CSS
      • Cascading Style Sheets support the separation of presentation from content
        • Information about fonts, colour, positioning etc is held in the style sheet.
      • Style Sheets often have some implicit semantics
        • This semantics is encoded in the names of the elements rather than in some formal structure.
        • Use of terms like header , footer or nav
        • Layout and presentation can add implicit meaning
    • SADIe
      • Semantics are implicitly encoded within the visual presentation of the Web page
      • Cascading Style Sheets define the visual presentation of the pages within a Website
      • Defining the role of the Cascading Style Sheet element, by association, defines the role of the Web page element
      • Gain the best of both worlds
        • Accurate transcoding in the same manner as Semantic Transcoding
        • Element definitions of a single CSS can be applied to multiple Web pages in a manner similar to Heuristic Transcoding
    • Annotating The CSS Upper Level Ontology Extended Ontology SADIe Application cnnCeilnav cnnBodyText cnnBottomNav cnnCSS
    • SADIe Implementation
      • Implemented as a proxy
        • All browsing requests from the client pass through the proxy, where transformation takes place.
        • Proxy rewrites HTML pages to provide accessible version of content
      • Allows users to:
        • Defluff – Removing non-essential elements
        • Re-order – Promoting elements that are considered important to the top of the page
        • Toggle Menus – Show/hide navigational menus
      SADIe Application
    • SADIe Transcoder
    • SADIefied CNN
    • Evaluation
      • We want to show that using SADIe decreases the time it takes to find information on the page
      • Four methods of testing information retrieval on Web pages:
        • Simple Fact Question : Involves the user finding a fact on the that is either true or false.
        • Judgement Question : Involves the user viewing a Website and providing a judgement
        • Comparison Of Fact Questions : Involves the user finding a series of facts and then answering a question that is either true or false.
        • Comparison Of Judgement Questions : Involves the user viewing a Website, comparing the facts and reaching a conclusion.
    • Evaluation Hypothesis
      • H0 :– The time it takes to complete a fact based task on a Webpage is the same regardless of whether the page that is used is SADIefied.
      • H1 :– The time it takes to complete a fact based task on a Web page using a SADIefied page is less than the time it takes to complete a task using a non-SADIefied page.
    • Evaluation Methodology
      • 20 pages that had similar content that was predominantly text based
        • News e.g. CNN, BBC, New York Times…
        • Blogs e.g. Blogger, Xanga…
      • Asked the user to find facts that were as similar for each page possible
        • Eg for news sites “What is the headline of the first story?”
      • The user was presented with a page one at a time, some of which were SADIefied
      • We timed how long it took the user to answer the question
    • Evaluation Results
      • So far we have evaluated SADIe with a single user
      • Results are encouraging and are significant using Randomization Testing…
      • … but we would like more users to support our results.
    • Further Work
      • This is still preliminary work, and much remains to do
      • Analysis of coping strategies
        • Informing our transformations and transcodes
      • (Semi)-Automation of mappings for stylesheets
      • Richer upper level ontology
        • Currently the ontology is essentially a taxonomy
      • More User Evaluations
    • Conclusions
      • Browsing the Web can be difficult for those who are visually impaired
      • SADIe can apply transcoding by using implicit information extracted from the CSS
      • Initial evaluation results are promising and show that SADIe can help visually impaired users reach content more quickly
      • More work still needs to be done
    • Questions? http://www.cs.manchester.ac.uk/img/sadie