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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 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.
Citation preview
Exposing Semantics To
Drive Transcoding
Darren Lunn, Sean Bechhofer and
Simon Harper
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
3/28
The Web
• Focuses on Presenting Information in a
Visual Manner
– Images
– Columns
– Chunks
• Some Knowledge is only Available
Implicitly from the Page Rendering
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Implicit Knowledge
Advertisement
Banner
Menu
Main Content
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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
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Accessing CNN In Audio
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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
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SADIe Approach
Banner
Banner
Menu
Headline Story Overview
Tabs
Advertisement
Image
Main Story
Heading
Story Overview
Main Story
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Original Annotation Solution
• Use an Ontology as an Abstraction to
represent Basic Concepts Appearing in
the Page
• Annotate the CSS Rather than the Page
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Proposed Solution
HTML
CSS
OntologyTransformed
Page
Rendered
Page
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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
12/28
Architecture
Application
HTMLCSS
Upper Ontology
Site-Specific Extension
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
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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
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Application Functionality vs.
Semantic Structure
SADIe
Removable NonRemovable
Priority Menu
Medium LowHigh
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Application Functionality vs.
Semantic Structure
Menu
Removable
High Priority
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
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Why Separate
• Adds Flexibility to the Overall
Application
• Adds Flexibility to the Overall Approach
• Easier For Designers to Construct
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General Relationships
• CNN_AdBox is Contained Within a
2ColumnFloat
• 2ColumnFloat is Removable Therefore
CNN_AdBox is Removable
• What If CNN_AdBox is Not Removable?
<pclass=“2ColumnFloat”>
<divclass=“CNN_AdBox”>...</div>
</p>
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Class Containment
High Priority Removable
CNN_AdBox 2ColumnFloat
isContained Within
hasPriority isRemovable
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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
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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
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Be Pragmatic
• Designers are Not Ontology Engineers
• Significant Overhead Will Hinder
Adoption
• Balance Between Minimal Effort but
Enough Knowledge to not be Hindered
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New SADIe Architecture
Application
HTMLCSS
Structural Ontology
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CSS Role Property
• 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
2ColumnFloat{
-uom-structural-role:LinkedMenu;
...
}
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Benefits
• Less Overhead to Expose Semantics
• Non Destructive
• Still Provide Same Functionality
– New Transformations being Investigated
• Other Uses of the Exposed Semantics
– AiSC
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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
