EXSLT

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EXSLT

• Facilitating the Standards Process

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Overview

• Jim Fuller (jim.fuller_at_webcomposite.com)
• Problem Year 2000, portability, functionality in
  XSLT
• Solution EXSLT
• Where we got it right/wrong
• Benefit
• Open Source Specification
• Future for EXSLT

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Problem in XSLT, around the Year 2000

• XSLT 1.0 processors were implementing extension
  functionality
• XSLT becoming dependent on underlying processor
• Reduced compatibility
• Other problems XSLT was limited, basic usage was
  being hampered by RTF

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History

• April 2000 Stephen Meunch
• Don Park XTECH2000 and David Megginson (of SAX
  fame)
• W3C reacted with XSLT1.1 e.g. xslscript
• Early 2001, Uche Ogbuji generated a petition
• Dr. Jeni Tennison formulated a set of draft specs

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Solution Extensions for XSLT

• March 2001, Dr. Tennison and small subset of
  community went about defining EXSLT
• EXSLT defines functions grouped into modules
• Where possible we created implementations either
  in pure XSLT 1.0 or using javascript
• Created documentation to assist users and
  implementators
• It was hoped that XSLT processor implementators
  would create native implementations

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EXSLT Modules

• Common Dramatically simplified stylesheets
  through providing a node-set(), object-type(),
  and document() (as per XSLT 1.1) function
  definitions
• Date and Time A full range of date and time
  handling functions.
• Dynamic Enables dynamic evaluation of XPATH
• Sets Encapsulated functions which make it easy
  to perform set type operations on XML.
• Functions Enabled the creation of functions
• Math Enables basic math operations within
  XSLT
• Random Added facilities to generate random
  numbers
• Regular Expressions Enabled regular
  expression handling
• Strings Contains string handling functions
  such as tokenize() and find() / replace().

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EXSLT Implementations

• Saxon
• 4suite
• Libxslt
• Xalan
• EXSLT.NET (now in Mvp.Xml)
• sablotron

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Where we got it wrong

• No one uses Function module
• Didnt follow Software development practices
• Module and function level imports fundamentally
  broken

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Function Module

• Underestimated the power of templates
• Lots of energy went into the discussion
• Originally intended to provide an EXSLT Function
  implementation of every extension

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Lack of Rigor

• Placing EXSLT with sourceforge would have been
  smart from the beginning
• Heavyweight XML markup allowed us to get away
  with standard software development practice
• Having no continuous integration or source
  control in place, very bad and paying the price
  today

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Import XSLT

• Importing was brokenwas no easy way for users
  to use module level imports
• Due to the fact of importing all implementations
  e.g. if msxslscript element was encountered by
  XSLT processor that didnt understand the
  element.

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Other Nagging Issues

• Interdependencies
• Function Submission process
• Missed opportunities
• Licensing
• Namespaces

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Getting things right

• Catering to users, implementators and eventually
  specification
• Having individuals like Jeni Tennison and Michael
  Kay involved
• Extensive documentation
• Inclusion of use cases

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Lessons Learned managing a large XML distribution

• Large XML distributions benefit from the re-use
  of existing markup/vocabularies like RDF and
  Dublin Core
• Just because its markup doesnt mean give up
  software development practices!
• RDF made revision easy everywhere
• Didnt need typing / XML Schemathough next time
  around

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Some Ruminations

• EXSLT was created by the entire XML community
• As with success on software projects, having
  individuals who are highly experienced and
  skilled has a major impact (Jeni Tennison, Uche
  O., Michael Kay)
• Synchronicity with XSLT UK 2001

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EXSLT informed XSLT 2.0

• Working with RTF
• XSLT is not a programming language
• Abstracted complex XSLT (grouping)
• Multiple Documents
• String Handling
• Evaluating XPATH?

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EXSLT informed XSLT 2.0

• Working with Result Tree Fragments
• XSLT is not a programming language
• Abstracted complex XSLT
• Outputting Multiple Documents
• String Handling
• Evaluating XPATH ???

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Benefits to XSLT 2.0

• Allowed XSLT 2.0 to take a bit longer
• Provided W3C Working Group with real world
  evidence (e.g. XSLT 2.0 functions are not 1st
  class)
• XSLT 2.0 and the suite of linked specifications
  puts EXSLT as we know it out of business

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EXSLT Future

• EXSLT as a specification has done its job and
  should die a natural death
• XSLT 1.0 usage will peak, which is why I have
  submitted a complete build based on Ant which
  generates site document, platform specific module
  imports, and reports on XSLT processor
  compatibility up to the rest of the EXSLT gang
  to review
• Possible XSLT 2.0 function library?
• Does EXSLT have application beyond XSLT ?

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Facilitation

• EXSLT came from the whole XSLT community
• EXSLT was a bridge between groups like the W3C
  and the community
• EXSLT goals were constrained and focused on what
  was important rather then completeness
• Why are there not more of these style efforts
  bridging the problem gap e.g. etc..

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Open Source Specification

• Micah Dubinko recent open letter to WHATWG
  illustrates the point
• Are there tools that can help us (developers)?
• working on schema enabled wiki with annotation

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Conclusion

• Suggestionsuse cases, informal spec review,
  early implementation
• Linking in XML, XML Schema, Xform, WS, Binary
  XML, What to do with XML Namespaces.
• Thank you