XSLT II

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XSLT II

• Robin Burke
• ECT 360

2
Outline

• Conditionals
• Numbering
• Functions and operators
• Variables and parameters
• Named and recursive templates

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Conditional nodes

• XSLT supports two kinds of conditional elements
• ltxslifgt
• ltxslchoosegt
• If is only if-then (no else)
• Choose is more general

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Example

• if
• choose

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Comparison operators
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Predicates

• XPath expressions
• test for a condition
• result set of nodes that fulfill that condition

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Example

• from last week

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Numbering

• Number nodes using
• ltxslnumbergt
• position()
• Using position()
• Nodes are numbered by position in result document
• Can be used in conditional statements

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Number element

• Nodes are numbered according to position in
  source document
• Attributes
• valueexpression any XPath expression that
  evaluates to a number (i.e. position())
• countpattern specifies which nodes to count
• leveltype tree level for nodes to count can be
  any, single, or multiple

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USING ltXSLNUMBERgt

• Attributes
• frompattern pattern indicates where numbering
  should restart
• formatpattern pattern indicates number format
• grouping-size, grouping-separator indicate how
  digits are grouped and separator character

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Example

• numbering

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XPath numerical functions
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XPath string functions
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XPath operators
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Example

• Calculating the average

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Number format

• XPath function format-number
• Syntax format-number(value, format)
• Example format-number(56823.847, ',0.00')
  displays 56,823.85

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Number format syntax
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Decimal format

• XSL element for defining number formats
• Named decimal format passed as argument to
  format-number

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Variables

• Not variable!
• User-defined name that stores a particular value
  or object
• Types
• number
• text string
• node set
• boolean
• result tree fragment

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Using variables

• Syntax ltxslvariable namename
  selectvalue/gt
• Example ltxslvariable nameMonths select12
  /gt
• Names are case-sensitive
• Value only set once upon declaration
• Enclose text strings in single-quotes

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Using variables

• Value can be XPath expression
• Value can be XML fragment
• Syntax
• ltxslvariable nameLogogt
• ltimg srclogo.gif width300 height100
  /gt
• lt/xslvariablegt

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Variable reference

• Syntax variable-name
• Example Months
• Referencing tree fragments
• Do not use variable-name
• Use ltxslcopy-ofgt to reference value

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COPYING
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Global variables

• Can be referenced from anywhere within the style
  sheet
• Must be declared at the top level of the style
  sheet, as a direct child of the ltxslstylesheetgt
  element
• Must have a unique variable name
• Evaluated only once when stylesheet is invoked

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Local variables

• Referenced only within template
• Can share name with other local or global
  variable
• Reevaluated when template is used

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Examples

• average
• numbering

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Parameters

• Similar to variables, but
• Value can be changed after it is declared
• Can be set outside of scope
• Syntax ltxslparam namename selectvalue/gt
• Example ltxslparam nameFilter select'C103'
  /gt
• To reference param-name

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External parameters

• Depends on XSLT processor
• Some work by appending parameter value to url
• Command line processors allow external parameter
  setting
• MSXML
• Saxon

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Template parameters

• Local in scope
• Created inside ltxsltemplategt element
• Used to pass parameters to template

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Idea

• Called template
• contains param definitions
• Calling template
• place ltxslwith-paramgt element in
  ltxslapply-templatesgt element
• or ltxslcall-templategt element
• Syntax ltxslwith-param namename
  selectvalue/gt
• No error if calling param name does not match
  template param name

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Named template

• Template not associated with node set
• Collection of commands that are accessed from
  other templates in the style sheet
• Syntax
• ltxsltemplate name"name"gt
• XSLT elements
• lt/xsltemplategt

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Calling named templates

• Syntax
• ltxslcall-template namenamegt
• ltxslwith-param /gt
• ltxslwith-param /gt
• ...
• lt/xslcall-templategt

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Example
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Functional programming

• Functional programming language
• Relies on the evaluation of functions and
  expressions, not sequential execution of commands
• Different from C family of languages
• LISP, Scheme, ML

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Templates as functions

• A template supplies a result fragment
• incorporated into the final document
• think of this as substitution
• function call replaced by result

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Iteration

• How to handle iteration with templates?
• stars for ratings
• Possibilities
• convert numbers into node sets
• weird since node sets are supposed to come from
  the document
• recursive templates

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Recursion

• Recursion
• base case
• when do I stop?
• recursive case
• how do I bite off one piece
• call template again with the rest

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Example

• Template star(rating)
• desired output stars in rating
• Base case
• rating 0
• output nothing
• Recursive case
• rating gt 0
• output plus result of star (rating-1)

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Example, cont'd

• star(3)
• replaced by star(2)
• replaced by star(1)
• replaced by star(0)

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Pseudocode

• stars (n)
• if n 0 return ''
• else
• return '' stars(n-1)

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Recursive pattern

• Syntax with ltxslifgt
• ltxsltemplate nametemplate_namegt
• ltxslparam nameparam_name
  selectdefault_value /gt
• ...
• ltxslif teststopping_conditiongt
• ...
• ltxslcall-template nametemplate_namegt
• ltxslwith-param nameparam_name
  selectnew_value /gt
• lt/xslcall-templategt
• ...
• lt/xslifgt
• lt/xsltemplategt

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Example
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Another example

• "best rated" jeep supplier
• Finding maximum
• built into XSLT 2.0

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Recursive statement?
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What about the name?
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Homework 5

• Case 1 from Chapter 7
• Plus doing it "correctly" with CSS