Using XML, XSLT, and CSS in a Digital Library

1
Using XML, XSLT, and CSS in a Digital Library

• Rendering
• Using XSLT and CSS
• Mathematics Rendering
• Thomas Habing
• thabing_at_uiuc.edu
• ASIS Annual Meeting 2000

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Evolution of Rendering

• Full-text
• 96 Plugins Adobe Acrobat (PDF) or Softquad
  Panorma (SGML)
• 99 Custom Server-side Converter to DHTML
• 00 Standards-based XSLT Converter to DHTML
• Metadata
• 96 OpenText Livelink for short long citations
• 98 Merged with full-text
• 99 XSLT for long citations
• 00 Migrating to XSLT for long short citations
• Including special characters, formatting, and math

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XSLT Where Should It Happen

• Client-side
• IE5 only
• Not Netscape 6 or Mozilla (yet)
• IE5 not yet fully compliant w/ XSLT and XPath
  standard
• Can reduce the load on your servers
• But performance on low-end clients can be BAD
• Server-side
• Performance could be a problem on busy servers,
  serving large, complex documents
• More control flexibility over the conversion
  (metamerge)
• Offline Preconversion
• Best performance
• Not best for dynamic documents (metamerge)

4
Transform Source XML into HTML or Renderable
XML?

• Our current choice is HTML (XHTML)
• Many browsers do not support XML at all
• Even of the browsers that do support XML, they
  still support HTML better
• Images, Linking, Tables, CSS, etc.
• As there is more support for additional XML
  standards, such as XLink, this may not always be
  the case
• Even for renderable XML, we still need to
  revert to embedded HTML for some constructs
• Eliminates the need to for dual code maintenance

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Converting XML to HTML

• Simple one-to-one conversionsltsectgt becomes
  ltspan class"sect"gt
• span.sect displayblockmargin-left2em
• Attribute based conversionsltemph type"1"gt
  becomes ltspan class"emph_1"gt
• span.emph_1 font-styleitalic
• Generated text, such as punctuationltaggtltaugtTomlt/
  augtltaugtTimlt/augtltaugtBoblt/augtlt/aggt becomes Tom,
  Tim, Bob.
• Rearranged childrenltaugtltsngtHabinglt/sngtltfngtTomlt/f
  ngtlt/augt becomes Tom Habing

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Converting XML to HTML (cont.)

• Some elements are converted into HTML elements
  other than ltspangt or ltdivgt
• Figures are converted to ltimg src""gt tags.
• Internal links with ID and IDREF attributes are
  usually converted into HTML anchor tags.
• Table elements are converted into corresponding
  HTML lttablegt, lttrgt, or lttdgt tags.
• Real DTDs require some fairly complex
  processing.
• So far XSLT seems to be able to handle nearly
  every case we have come across
• However, some cases have required JScript
  extensions to XSLT

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Alternates to XSLT

• Custom Parser (our previous approach)
• SAX - Simple API for XML
• Performance can be better for large XML files
• Streaming parser - entire document is not loaded
  into memory as with XSLT
• Not as flexible as XSLT
• More difficult to rearrange output
• Not a W3C standard

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Rendering Mathematics

• SGML ISO 12083 or variant
• Convert to DHTML for native browser rendering
• Convert to an Image
• Convert to MathML and...
• Render as above, but only one target
• Render with a Plugin (techexplorer, WebEQ)
• Native browser support (Mozilla or Amaya)
• TeX
• Convert TeX to Image (tex-gtdvi-gtps-gtgif)
• Render with a Plugin (techexplorer)

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Rendering SGML Math as DHTML

• XSLT Dynamically Converts Markup to HTML with
• CSS Positioning
• JavaScript
• Dynamic Properties
• Center Verticallytopexpression((this.offsetHeig
  ht-8)/2'px')
• Set the widthwidthexpression(Math.max(
  this.parentNode.children(1).offsetWidth,
  this.offsetWidth)'px')
• Attached Behaviors
• behaviorurl(center.htc)
• Currently only works with Microsoft IE 5

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Math Example Using DHTML

• span.fr positionrelativewidth1pxmargin-top
  expression(-(this.children(1).offsetHeight-8)
  'px)topexpression((this.children(1).offsetHei
  ght-8) 'px)
• div.nu border-bottom1px solid
  blacktext-aligncenterbehaviorurl(nu.htc)
• div.de text-aligncenterbehaviorurl(de.htc)

ltfrgt ltnugt1lt/nugt ltdegt2lt/degtlt/frgt
ltspan classfrgt ltdiv classnugt1lt/divgt
ltdiv classdegt2lt/divgtlt/spangt
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Convert SGML Math to Image

• Need to support less capable browsers
• How to convert?
• Display document in Internet Explore as DHTML
• Hide irrelevant information leaving only the
  formula
• Resize the display window to fit in the formula
• Trim blank and check if there is unknown symbol
• Capture the display window and convert the image
  to GIF/JPEG format.
• Process is fully automated (Visual Basic)

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Rendering MathML

• Original PDF from publisher
• Custom DHTML
• Mozilla M18
• Techexplorer(Netscape)
• Amaya

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Rendering Issues

• Special Character Support
• STIX
• Unicode
• Publisher Specific Entities
• Mathematics
• Better Native Browser Support for MathML
• Conversion of Legacy Math to MathML