Using Extensible Stylesheets XSLT

1
Using Extensible Stylesheets (XSLT)

• Dan Gunter
• DIDC Group
• 11 June 2001

2
Talk Outline

• Motivation
• XML background information
• High-level view of XSLT
• Example of use of XSLT for a real Web page
• Links to tools and more information

3
Motivation

• We need to share information about our work, and
  the Web is the medium of choice
• But updating and maintaining HTML pages every
  time the underlying data changes is tedious
• Changing the datas format is also tedious
• We need to separate content from presentation so
  that changing each is easier

4
XML Overview

• XML uses nested elements that look like HTML,
  i.e. ltelementgtdatalt/elementgt
• But in XML, you, the document creator, can invent
  your own elements
• Sample XML fragment
• ltaddressgt
• ltnamegtDan Gunterlt/namegt
• ltstreetgt13 Foobar Avelt/streetgt
• ltcitygtSan Franciscolt/citygt
• ltstategtCAlt/stategt
• lt/addressgt

5
Well-formed vs. Valid XML

• If start-tags match end-tags and the special
  characters (like lt and gt) are used properly,
  a document is well-formed.
• If the document is well-formed and it also
  conforms to its schema or document type
  definition (DTD), it is called valid.

well-formed, not valid address
valid address
ltaddressgt ltnamegtJoelt/namegt
lthairgtbrownlt/hairgt lteyesgtgreenlt/eyesgt
ltheightgt70lt/heightgt lt/addressgt
ltaddressgt ltnamegtJoelt/namegt ltstreetgt1 Odd
Stlt/streetgt ltcitygtTrentonlt/citygt
ltstategtNJlt/stategt lt/addressgt
6
XSLT

• Stands for Extensible Stylesheet Language
  Transformation
• It is a script language specifically designed for
  transforming XML documents into other documents
  (HTML, text, PDF, etc.)
• The XSLT language is expressed in XML, and its
  syntax is specified by an XML schema
• Thus, each XSLT script is a valid XML document

7
XSLT Hello, world!

• ltxslstylesheet version1.0
• xmlnsxslhttp//www.w3.org/1999/XSL/Transformgt
• ltxsloutput methodhtml/gt
• ltxsltemplate match/gt
• lthtmlgt
• ltbodygt
• Hello, world!
• lt/bodygt
• lt/htmlgt
• lt/xsltemplategt
• lt/xslstylesheetgt

8
Transformation Pipeline
well-formed XML document
XSLT
XML
valid XSLT document
processors exist in many languages, and can be
used from the command-line or with an API
XSLT processor
the format of the output depends on the
stylesheet used
output
9
Transformation Concepts
Think of the input XML document as a tree of
elements. XSLT can select elements and then
extract their values
person
name
age
gender
M
first
middle
last
30
Lazy
Programmer
Q.
into the output document.
10
Example

• Example task
• Applying XSLT to the task

11
Example task

• Data A list of documents for a Grid Forum
  working group, each with an author, title,
  document, version, date, status, notes, and an
  associated PDF file named by the document
• Output Sorted table(s) of the documents on the
  groups website, with hyperlinks to the actual
  files. Like this.

12
Applying XSLT to the task

• Put the data into XML document(s).
  documents.xml
• Write stylesheet(s) documents.xsl
• Write a small script to automate the process of
  feeding the document(s) to an XSLT processor
  xslt.html
• Run the script

13
When not to use XSLT

• XSLT is probably not worth it for small, one-shot
  jobs, i.e. when
• Number of data items is small
• Formatting is unlikely to change very often
• Only one output format will be needed in the
  foreseeable future

14
When to use XSLT

• XSLT is great for frequently updated data
  because
• Easy to change formatting for whole document
  (e.g. change order of TABLE columns)
• Easy to create alternate views of the same data
• Data more readable (not buried in HTML)
• Easier to automate related tasks (e.g. inactive
  document email script)

15
Links and Tools

• Xalan, from the Xerces project at Apache
  (http//xml.apache.org)
• 4XSLT from 4Suite (http//4suite.org)
• Google search for xslt, click on
  XSLImplementations category
• XML Bible page on XSLT (http//www.ibiblio.org/xml
  /books/bible/updates/14.html)