Dynamic Accessibility

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Dynamic Accessibility

• Nick PooleICT AdviserResource The Council for
  Museums, Archives and Libraries

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Contents

• Introduction
• Static-page accessibility
• Dynamic accessibility - key concepts
• XHTML 1.1
• Cascading Style Sheets
• XML accessibility
• New technologies - SMIL, VRML, SVG
• e-Books and TTS
• Contact details

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Introduction

• What is accessibility?
• Technological accessibility
• browsers, platforms, operating systems, plugins,
  screen resolutions
• Intellectual accessibility
• navigation, language, structure, search tools,
  URL
• Physical accessibility
• design, layout, contrast, font size, text
  versions of animated/interactive information

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Static-page accessibility

• Proper use of existing accessibility features in
  HTML
• Separation of content from presentation - CSS and
  graceful transformation
• Logical in-page reading order
• Logical in-site navigational structure
• Thinking about visual presentation - contrast,
  layout etc
• http//www.w3c/prg/WAI

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Dynamic accessibility - key concepts

• Very similar...
• Separation of style from content
• Enabling dynamic re-flowing of content to address
  different platforms and technologies
• Clean code properly implemented
• The benefits and dangers of XML
• Making use of existing accessibility features
• Validate wherever possible
• Universal design and user-oriented publishing

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XHTML 1.1

• The Extensible HyperText Markup Language
  (XHTML) is a family of current and future
  document types and modules that reproduce,
  subset, and extend HTML, reformulated In XML.
• 3 flavours
• strict - clean structural markup
• transitional - XHTML elements plus support for
  backwards-compatibility
• frameset - for creating pages subdivided into
  frames

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XHTML 1.1 and Accessibility

• Well-formed XHTML pages follow a strict set of
  rules and avoid the use of non-standard markup
• XHTML supports graceful transformation between
  platforms - eg PC, PDA, braille
• Strict rule-based approach ensures better
  compatibility across browsers
• Imposes uniformity on document structure
• Keep pace with tech development
• Migrate existing documents from HTML using
  HTMLTidy - http//www.w3.org

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Cascading Style Sheets

• CSS separates document structure (content) from
  presentation (style)
• Prevents the use of structural HTML tags to
  define layout
• Positioning properties avoid further use of
  markup to define layout
• Allows the user to override the server-side CSS
  with their own preferences
• Supports features which help orientation
• Support for Aural Style Sheets (ACSS)
• Better presentation of ALT content

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XML Accessibility

• An XML schema is accessible if it enables, and
  indeed actively promotes, the creation of
  accessible documents
• and
• A document is accessible if it can be equally
  understood by its target audience regardless of
  the device used to access it
• XML Accessibility Guidelineshttp//www.w3.org/T
  R/xag.html

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XML Accessibility

• 2 key concepts
• Semantic-rich schema that support accessibility
• Device independence - write once, deliver through
  different channels

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XML Accessibility

• Facilitate the provision of ALT descriptions for
  different types of content
• Apply the summary and caption elements
  provided for tables in XHTML
• lttable border1 summaryThis table provides a
  list of names, addresses, telephone numbers and
  email addresses for club membersgt
• ltcaptiongtltemgtContact detailslt/emgtlt/captiongt
• lttrgtltthgtlt/trgtlttrgtlttdgtlt/trgtlt/tdgt
• lt/tablegt

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XML Accessibility

• Standard mechanisms exist for linking and
  pointing in XML
• Make use of XLink and Xpointer instead of
  creating your own mechanisms (which may not be
  recognised/supported)
• ltcrossref xmlnsxlinkhttp//www.w3.org/1999/xlin
  k
• xlinkhrefhttp//www.resource.gov.uk/file.xmlgt
• Link text
• lt/crossrefgt

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XML Accessibility

• Using the flexibility of XML to define element
  types that identify important text content
• Certain elements are more important than others
  in identifying and assessing the content of a
  document
• When creating a tagset, include semantic tags
  which allow you to identify these important
  elements
• In addition to identifying tags, include
  additional descriptive semantics

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XML Accessibility

• When identifying important descriptive elements,
  make use of standard mechanisms/namespaces where
  possible (eg Dublin Core/RDF)
• ltrdfRDF
• xmlnsrdfhttp//www.w3.org/1999/02/22-rdf-syntax
  -ns
• xmlnsdchttp//www.purl.org/dc/elements/1.1/gt
• ltrdfDescription about http//www.peoplesnetwork
  .gov.ukgt
• ltdcTitlegtlt/dc.Titlegt
• ltdcDescriptiongtlt/dc.Descriptiongt
• ...etc...

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XML Accessibility

• Semantic consistency
• Ensure that the same element contains the same
  content throughout the document - do not re-use
  elements for different purposes
• When re-using modules from elsewhere, ensure that
  you apply their elements as intended

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XML Accessibility

• Using XML to design for platform-independence
• Provide default style-sheets for output to
  different platforms/devices (CSS or XSLT)
• Create element types that allow classification
  and grouping into logical, navigable document
  structures
• Provide ways of interacting with the document
  that are device-independent
• Allow the user to control the timeframe within
  which events occur

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XML Accessibility

• Final points.
• Document the semantics and structure of your XML
• Provide a machine-understandable way of
  retrieving this documentation (eg. by using the
  xsischemaLocation attribute)
• Provide human-understandable definitions for the
  semantics of your XML elements (eg. by using the
  xsdannotation attribute)
• Where accessible elements have been provided,
  ensure that these are documented

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New technologies - SMIL

• Synchronised Multimedia Integration Language
• Specific issues
• Alternative equivalent content
• Alternatives have to be synchronised with primary
  media
• Multiple sensory channels (sight, hearing, touch)
• Content changes without user interaction leading
  to disorientation

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New Technologies - SMIL

• Alternative equivalent content
• Text transcription - alt, title, abstract,
  longdesc
• Auditory descriptions
• Synchronised captions - textstream,
  system-captions (where enabled)
• Multilinguality - textstream captions in one
  language, overdub audio descriptions in another
• Use of the switch element to allow the user to
  select their preferred channel

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New Technologies - SMIL

• Use SMIL in conjunction with CSS to provide
  screen layouts that transform (eg. percentage
  areas for onscreen captioning)
• Use the title attribute to describe the nature
  of all SMIL elements
• Consider providing a temporal navigation bar to
  enable user interaction with time-dependent
  content
• Use the system- test attributes to re-purpose
  content to user preferences

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New Technologies - VRML

• Range of built-in features to enhance access
• 2 levels of alternative textual description -
  Worldinfo and Anchor nodes
• audio cues including spoken descriptions,
  proximity-sensitive effects and
  trigger/viewpoint-specific events
• mapping to external input devices to facilitate
  navigation
• Utilities available to enable access
• showVP, addSndToVrml and speakWorldInfo
• essentially providing context/viewpoint info to
  assist the user
• http//ovrt.nist.gov/projects/VRMLaccess/

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New Technologies - SVG

• Scalable Vector Graphics
• XML-based image format
• Range of accessibility features
• scalable!
• Includes a text description for each logical
  component of an image
• images are encoded as plain text
• SVG images can be encoded into XML documents
• Can also call images from other documents using
  xLink
• Images can be re-flowed to suit different media
• Improved support for metadata

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e-Books and Text-to-Speech

• Conflict between XML encoding and Digital Rights
  Management information
• XML encoding supports user-controlled
  text-to-speech delivery (Open e-Books Publication
  Structure)
• DRM protection blocks delivery through these
  channels
• Ongoing debate at http//www.openebook.org

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Contact

• Nick Poole
• ICT Adviser
• Resource The Council for Museums, Archives and
  Libraries
• 16 Queen Annes Gate
• London SW1H 9AA
• Email nick.poole_at_resource.gov.uk
• Web http//www.peoplesnetwork.org.uk
• Telephone [phone]