Exposing Semantics to Drive Transcoding

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The World Wide Web (Web) is a visually complex, dynamic, multimedia system that can be inaccessible to people with visual impairments. SADIe uses semantic annotations of a Website's Cascading Style …

The World Wide Web (Web) is a visually complex, dynamic, multimedia system that can be inaccessible to people with visual impairments. SADIe uses semantic annotations of a Website's Cascading Style Sheet (CSS) to drive a transformation process that can improve access to content for visually impaired users. The original process of annotating the CSS involved the use of an upper ontology, extended by a site specific lower ontology. While this approach provided rich annotation of the CSS terms, experience suggests that components within the model were inappropriate for the interactive system we were developing. This experience has led to a more pragmatic approach that still provides the necessary semantics required to drive the SADIe transcoding tool, but in a more lightweight manner. This paper describes the lessons learnt from building the ontological models for the SADIe platform, highlighting pitfalls that developers of ontologies in interactive systems should be wary of.

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  • 1. Exposing Semantics To Drive Transcoding
    Darren Lunn, Sean Bechhofer and Simon Harper
  • 2. 2/28
    Summary
    Visual Rendering Can Provide Semantic Information
    Semantics Can Be Used to Drive a Transformation Process
    Poor Design Decisions Can Hinder Flexibility and Adoption
    A Well Defined Model and a Little Pragmatism Goes a Long Way
  • 3. 3/28
    The Web
    Focuses on Presenting Information in a Visual Manner
    Images
    Columns
    Chunks
    Some Knowledge is only Available Implicitly from the Page Rendering
  • 4. 4/28
    Implicit Knowledge
    Advertisement
    Banner
    Menu
    Main Content
  • 5. 5/28
    Assistive Technology
    Visually Impaired Users use Assistive technologies e.g. Screen Readers
    Render Pages Sequentially in Audio
    Achieved by Accessing the Underlying HTML
    Focus on Visual Presentation Rather than Content Hampers This
    Particularly if Attention is Not Paid to Coherent Design
    Subtleties of Visual Presentation Can be Lost
  • 6. 6/28
    Accessing CNN In Audio
  • 7. 7/28
    Screen Readers
    Traversal of Content is Serial
    Top-to-bottom
    Left-to-Right
    Important Information may not be Encountered Until Later On.
    Information Such as Menus may be Repeated for Every Page
    Tiresome if the User has to Wait for the Menu for Each Page
  • 8. 8/28
    SADIe Approach
    Main Story
    Heading
    Banner
    Menu
    Banner
    Story Overview
    Headline
    Story Overview
    Main Story
    Tabs
    Advertisement
    Image
  • 9. 9/28
    Original Annotation Solution
    Use an Ontology as an Abstraction to represent Basic Concepts Appearing in the Page
    Annotate the CSS Rather than the Page
  • 10. 10/28
    Proposed Solution
    Ontology
    Transformed
    Page
    HTML
    Rendered
    Page
    CSS
  • 11. 11/28
    Two-Part Ontology
    An Upper Ontology Provides Basic Information about Authoring Concepts
    This is Extended to Provide information about Particular Style Sheets
    The Definitions in these Ontologies Provide the Annotation of the CSS Elements
  • 12. 12/28
    Architecture
    Application
    Upper Ontology
    Site-Specific Extension
    HTML
    CSS
  • 13. 13/28
    Overarching Aim
    Describe Semantic Structure of Websites
    Use Inference Engines to Determine Relationships Between Elements of the Website
    Transcode Website Based on these Relationships
  • 14. 14/28
    Success?
    Transcoding was Successful on a Diverse Range of CSS-based Sites
    User Studies Demonstrated the Usefulness of the Transformations
    But the Model had Weakness that Limited The Approach
  • 15. 15/28
    Application Functionality vs. Semantic Structure
    SADIe
    Removable
    NonRemovable
    Menu
    Priority
    Low
    Medium
    High
  • 16. 16/28
    Application Functionality vs. Semantic Structure
    Menu
    High Priority
    Removable
  • 17. 17/28
    Separate Functionality From Domain Knowledge
    We Advocate Separation of Structure (HTML) from Presentation (CSS)
    Also Separate Knowledge from Application Functionality
    Split Ontology Into Two
    Push More Computation into the Application
  • 18. 18/28
    Why Separate
    Adds Flexibility to the Overall Application
    Adds Flexibility to the Overall Approach
    Easier For Designers to Construct
  • 19. 19/28
    General Relationships
    <pclass=“2ColumnFloat”>
    <divclass=“CNN_AdBox”>...</div>
    </p>
    CNN_AdBox is Contained Within a 2ColumnFloat
    2ColumnFloat is Removable Therefore CNN_AdBox is Removable
    What If CNN_AdBox is Not Removable?
  • 20. 20/28
    Class Containment
    High Priority
    Removable
    hasPriority
    isRemovable
    CNN_AdBox
    2ColumnFloat
    isContained Within
  • 21. 21/28
    Only Within That Instance
    CNN_AdBox is Contained Within a 2ColumnFloat Only Within this Instance
    CSS Properties Can Still be Applied Even If CNN_AdBox is Not Contained Within 2ColumnFloat
  • 22. 22/28
    A Little Testing Goes A Long Way
    Small Scale Testing Brings to Light Errors of Modelling
    Can not Expect To Know Everything Without Real World Case Studies
    Prevents Effort of Reengineering
    Prevents Loss of Faith in the Tool
  • 23. 23/28
    Be Pragmatic
    Designers are Not Ontology Engineers
    Significant Overhead Will Hinder Adoption
    Balance Between Minimal Effort but Enough Knowledge to not be Hindered
  • 24. 24/28
    New SADIe Architecture
    Application
    Structural Ontology
    HTML
    CSS
  • 25. 25/28
    CSS Role Property
    2ColumnFloat{
    -uom-structural-role:LinkedMenu;
    ...
    }
    Add a New Role to the CSS
    Still Validates
    Explicitly States What the Class Represents
    Values Based on WAfA Ontology
    Ontology of Accessibility and Web Authoring Concepts
  • 26. 26/28
    Benefits
    Less Overhead to Expose Semantics
    Non Destructive
    Still Provide Same Functionality
    New Transformations being Investigated
    Other Uses of the Exposed Semantics
    AiSC
  • 27. 27/28
    Conclusion
    Visual Rendering Can Provide Semantic Information
    Semantics Can Be Used to Drive a Transformation Process
    Poor Design Decisions Can Hinder Flexibility and Adoption
    A Well Defined Model and a Little Pragmatism Goes a Long Way
  • 28. Questions
    http://hcw.cs.manchester.ac.uk