XSL: EXtensible Stylesheet Language

1
XSL EXtensible Stylesheet Language

• The World Wide Web Consortium (W3C) started to
  develop XSL because there was a need for an
  XML-based Stylesheet Language
• XSL describes how the XML document should be
  displayed

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XSL - More Than a Style Sheet Language

• XSL consists of three parts
• XSLT - a language for transforming XML documents
• XPath - a language for navigating in XML
  documents
• XSL-FO - a language for formatting XML documents

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XSLT XSL Transformations

• XSLT is the most important part of XSL
• XSLT transforms an XML document into another XML
  document, or another type of document that is
  recognized by a browser
• XSLT uses XPath to navigate in XML documents (to
  find elements and attributes)
• XSLT became a W3C Recommendation 16. November
  1999
• XSLT transforms an XML source-tree into an XML
  result-tree.

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Style Sheet Declaration

• In XML file
• lt?xml version"1.0" encoding"Big5"?gt
• lt?xml-stylesheet type"text/xsl"
  href"hello.xsl"?gt
• lthellogt Hello, World ! lt/hellogt

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In xsl file

• lt?xml version"1.0" encoding"Big5"?gt
• ltxslstylesheet version"1.0" xmlnsxsl"http//ww
  w.w3.org/1999/XSL/Transform"gt
• ltxsltemplate match"/"gt
• lthtmlgt
• ltheadgtlttitlegtFirst XSLTlt/titlegtlt/headgt
• ltbodygt
• lth2gtltcentergtltxslvalue-of select"hello"
  /gtlt/centergtlt/h2gt
• lt/bodygt
• lt/htmlgt
• lt/xsltemplategt
• lt/xslstylesheetgt

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• ltxslstylesheet version"1.0" xmlnsxsl"http//ww
  w.w3.org/1999/XSL/Transform"gt
• To get access to the XSLT elements, attributes
  and features we must declare the XSLT namespace
  at the top of the document.
• xmlnsxsl"http//www.w3.org/1999/XSL/Transform"
  points to the official W3C XSLT namespace.
• If you use this namespace, you must also include
  the attribute version"1.0".

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ltxsltemplategt Element

• An XSL style sheet consists of one or more set of
  rules that are called templates.
• Each template contains rules to apply when a
  specified node is matched

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• The match attribute is used to associate a
  template with an XML element.
• The match attribute can also be used to define a
  template for the entire XML document.
• The value of the match attribute is an XPath
  expression (i.e. match"/" defines the whole
  document).

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ltxslvalue-ofgt Element

• The ltxslvalue-ofgt element can be used to extract
  the value of an XML element and add it to the
  output stream of the transformation
• The value of the select attribute is an XPath
  expression. An XPath expression works like
  navigating a file system where a forward slash
  (/) selects subdirectories

10
ltxslfor-eachgt Element

• The ltxslfor-eachgt element allows you to do
  looping in XSLT.
• The XSL ltxslfor-eachgt element can be used to
  select every XML element of a specified node-set

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Filtering the Output

• We can also filter the output from the XML file
  by adding a criterion to the select attribute in
  the ltxslfor-eachgt element.
• ltxslfor-each select"catalog/cdartist'Bob
  Dylan'"gt
• Legal filter operators are
•   (equal)
• ! (not equal)
• lt less than
• gt greater than

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ltxslsortgt Element

• The ltxslsortgt element is used to sort the
  output.
• To sort the output, simply add an ltxslsortgt
  element inside the ltxslfor-eachgt element in the
  XSL file
• ltxslsort select"title" order"descending"/gt
• descending
• ascending
• The select attribute indicates what XML element
  to sort on

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ltxslifgt Element

• To put a conditional if test against the content
  of the XML file, add an ltxslifgt element to the
  XSL document.
• ltxslif test"expression"gt
• ... ...some output if the expression is
  
• true... ...
• lt/xslifgt
• The value of the required test attribute contains
  the expression to be evaluated.

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ltxslchoosegt Element

• The ltxslchoosegt element is used in conjunction
  with ltxslwhengt and ltxslotherwisegt to express
  multiple conditional tests.
• Syntax
• ltxslchoosegt
• ltxslwhen test"expression"gt
• ... some output ...
• lt/xslwhengt
• ltxslotherwisegt
• ... some output ....
• lt/xslotherwisegt
• lt/xslchoosegt

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ltxslapply-templatesgt Element

• The ltxslapply-templatesgt element applies a
  template to the current element or to the current
  element's child nodes.
• . with the select attribute to specify the
  current node.

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XPath

• XPath is a language for finding information in an
  XML document.
• XPath is used to navigate through elements and
  attributes in an XML document.
• XPath is a major element in the W3C's XSLT
  standard
• and XQuery and XPointer are both built on XPath
  expressions

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What is XPath

• XPath is a syntax for defining parts of an XML
  document
• XPath uses path expressions to navigate in XML
  documents
• XPath contains a library of standard functions
• XPath is a major element in XSLT
• XPath is a W3C Standard

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XPath

• XPath uses path expressions to select nodes or
  node-sets in an XML document.
• XPath includes over 100 built-in functions. There
  are functions for string values, numeric values,
  date and time comparison, node and QName
  manipulation, sequence manipulation, Boolean
  values, and more.

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XPath Nodes

• In XPath, there are seven kinds of nodes
  element, attribute, text, namespace,
  processing-instruction, comment, and document
  (root) nodes.

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XPath Syntax

• lt?xml version"1.0" encoding"ISO-8859-1"?gt
• ltbookstoregt
• ltbookgt
• lttitle lang"eng"gtHarry
  Potterlt/titlegt
• ltpricegt29.99lt/pricegt
• lt/bookgt
• ltbookgt
• lttitle lang"eng"gtLearning
  XMLlt/titlegt
• ltpricegt39.95lt/pricegt
• lt/bookgt
• lt/bookstoregt

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Selecting Nodes

• Nodename Selects all child nodes of the
  node/Selects from the root node
• // Selects nodes in the
  document from the current node that match the
  selection no matter where they are
• . Selects the current node
• .. Selects the parent of
  the current node
• _at_ Selects attributes

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Selecting Nodes

• Bookstore Selects all the child nodes of the
  bookstore element
• /bookstore Selects the root element bookstore
  Note If the path starts with a slash ( / ) it
  always represents an absolute path to an element!
• Bookstore/book Selects all book elements that
  are children of bookstore
• //book Selects all book elements no
  matter where they are in the document
• bookstore//book Selects all book elements
  that are descendant of the bookstore element, no
  matter where they are under the bookstore element
• //_at_lang Selects all attributes that
  are named lang

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Predicates

• Predicates are used to find a specific node or a
  node that contains a specific value.
• Predicates are always embedded in square brackets.

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• /bookstore/book1 Selects the first book
  element that is the child of the bookstore
  element
• /bookstore/booklast() Selects the last book
  element that is the child of the bookstore
  element
• /bookstore/booklast()-1 Selects the last but
  one book element that is the child of the
  bookstore element
• /bookstore/bookposition()lt3 Selects the first
  two book elements that are children of the
  bookstore element
• //title_at_lang Selects all the title elements
  that have an attribute named lang
• //title_at_lang'eng' Selects all the title
  elements that have an attribute named lang with a
  value of 'eng
• /bookstore/bookpricegt35.00 Selects all the
  book elements of the bookstore element that have
  a price element with a value greater than 35.00
• /bookstore/bookpricegt35.00/title Selects all
  the title elements of the book elements of the
  bookstore element that have a price element with
  a value greater than 35.00

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Selecting Unknown Nodes

• XPath wildcards can be used to select unknown XML
  elements
• Matches any element node
• _at_ Matches any attribute node
• node() Matches any node of any kind
• /bookstore/ Selects all the child nodes of the
  bookstore element
• // Selects all elements in the document
• //title_at_ Selects all title elements which
  have any attribute

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Selecting Several Paths

• By using the operator in an XPath expression
  you can select several paths
• //book/title //book/price Selects all the
  title AND price elements of all book elements
• //title //price Selects all the title AND
  price elements in the document
• /bookstore/book/title //price Selects all the
  title elements of the book element of the
  bookstore element AND all the price elements in
  the document

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XPath Axes

• An axis defines a node-set relative to the
  current node.
• Ancestor Selects all ancestors (parent,
  grandparent, etc.) of the current node
• ancestor-or-self Selects all ancestors
  (parent, grandparent, etc.) of the current node
  and the current node itself
• Attribute Selects all attributes of the current
  node
• Child Selects all children of the current
  nodedescendantSelects all descendants (children,
  grandchildren, etc.) of the current
  nodedescendant-or-selfSelects all descendants
  (children, grandchildren, etc.) of the current
  node and the current node itselffollowingSelects
  everything in the document after the closing tag
  of the current nodefollowing-siblingSelects all
  siblings after the current nodenamespaceSelects
  all namespace nodes of the current
  nodeparentSelects the parent of the current
  nodeprecedingSelects everything in the document
  that is before the start tag of the current
  nodepreceding-siblingSelects all siblings before
  the current nodeselfSelects the current node

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ltxslselectgt Element

• ltxslfor-each select"booklist/book_at_sales'Y'"gt