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TUTORIAL 7

TUTORIAL 7. CREATING A COMPUTATIONAL STYLESHEET (Using XSLT style sheet to calculate values based on data from the source document). OBJECTIVES. In this chapter you will: Learn how to number nodes Apply XPath functions such as count() and sum() Create formulas using mathematical operators

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TUTORIAL 7

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  1. TUTORIAL 7 CREATING A COMPUTATIONAL STYLESHEET (Using XSLT style sheet to calculate values based on data from the source document) New Perspectives on XML, 2nd Edition Tutorial 7

  2. OBJECTIVES In this chapter you will: • Learn how to number nodes • Apply XPath functions such as count() and sum() • Create formulas using mathematical operators • Work with text nodes and white space • Create variables and parameters New Perspectives on XML, 2nd Edition Tutorial 7

  3. OBJECTIVES In this chapter you will: • Create named and recursive templates • Work with multiple style sheets • Learn how to use extension functions and elements New Perspectives on XML, 2nd Edition Tutorial 7

  4. NUMBERING NODES • Goal: add numbers to the items in columns • Number nodes using: • Xpath’sposition() function • Position of the element in the result document • Can be used in conditional statements <xsl:if test=“position()=3 /> • XSLT <xsl:number> element <xsl:number select=“expression” /> New Perspectives on XML, 2nd Edition Tutorial 7

  5. Using the number Element Source document Style <xsl:for-each select=“products/item”> <xsl:number /> <xsl:value-of select=“.” /> <br/> </xsl:for-each> <products> <item>Goblin Fountain</item> <item>Tracer Fire</item> <item>Dragon Fountain</item> <item>Rock the Sky</item> <item>Pyro Blast</item> </products> Numbered list Goblin Fountain Tracer Fire Dragon Fountain Rock the Sky Pyro Blast New Perspectives on XML, 2nd Edition Tutorial 7

  6. Counting subset of items Source document Style <xsl:for-each select=“fountain”> <xsl:number /> <xsl:value-of select=“.” /> <br/> </xsl:for-each> <products> <fountain>Goblin Fountain</fountain> <rocket>Tracer Fire</rocket> <fountain>Dragon Fountain</fountain> <rocket>Rock the Sky</rocket> <rocket>Pyro Blast</rocket> </products> Numbered list 1. Goblin Fountain 2. Dragon Fountain New Perspectives on XML, 2nd Edition Tutorial 7

  7. Levels Source document Style <xsl:for-each select=“//item”> <xsl:number /> <xsl:value-of select=“.” /> <br/> </xsl:for-each> <products> <fountains> <item>Goblin Fountain</item> <item>Dragon Fountain</item> </fountains> <rockets> <item>Tracer Fire</item> <item>Rock the Sky</item> <item>Pyro Blast</item> </rockets> </products> Numbered list 1. Goblin Fountain 2. Dragon Fountain 1. Tracer Fire 2. Rock the Sky 3. Pyro Blast New Perspectives on XML, 2nd Edition Tutorial 7

  8. USING <XSL:NUMBER> • Nodes are numbered according to position in source document • Attributes: • select=expression: any XPath expression that evaluates to a number • count=pattern: specifies which nodes to count • level=type: tree level for nodes to count • any = across different levels as if they were all siblings • single = items at one level only (defaut) • multiple = hierarchy count New Perspectives on XML, 2nd Edition Tutorial 7

  9. Hierarchical numbered list Source document Style <xsl:for-each select=“//group | //item”> <xsl:number level=“multiple” count=“group | item” /> /> <xsl:vale-of select=“.” /> <br/> </xsl:for-each> <products> <group> <item>Goblin Fountain</item> <item>Dragon Fountain</item> </group> <group> <item>Tracer Fire</item> <item>Rock the Sky</item> <item>Pyro Blast</item> </group> </products> Hierarchical list 1. Fountains 1.2. Goblin Fountain 1.2. Dragon Fountain 2. Rockets 2.1. Tracer Fire 2. 2. Rock the Sky 2. 3. Pyro Blast1 New Perspectives on XML, 2nd Edition Tutorial 7

  10. USING <XSL:NUMBER> • Attributes: • from=pattern: pattern indicates where numbering should restart • format=pattern: pattern indicates number format • 1=integer (1, 2, 3,…) • A= alphabetical uppercase (A, B, C, …) • a= alphabetical lowercase (a, b, c, …) • i= lowercase Roman numerial (i, ii, iii, iv, v, …) • I= uppercase Roman numerial (I, II, III IV, V, …) • grouping-size, grouping-separator: indicate how digits are grouped and separator character. For example <xsl:number format=“1” grouping-size=“2” grouping-separator=“ ” /> displays “548710” as “54 87 10” New Perspectives on XML, 2nd Edition Tutorial 7

  11. WORKING WITH XPATH FUNCTIONS • Used to calculate numerical values or manipulate text strings • Numerical functions: Examples: <xsl: value-of select=“count(//customer)” /> <xsl: value-of select=“//@sum(qty)” /> New Perspectives on XML, 2nd Edition Tutorial 7

  12. XPATH TEXT FUNCTIONS New Perspectives on XML, 2nd Edition Tutorial 7

  13. XPATH STRING FUNCTION Example • Substring-before (“C101 C102 C103 C104”, “ ”) • Locates the first blank space in the text string and extracts all the text before the first blank, e.g., “C101” New Perspectives on XML, 2nd Edition Tutorial 7

  14. WORKING WITH MATHEMATICAL OPERATORS • Six operators: Example: <xsl:value-of select=“@qty * @price” /> New Perspectives on XML, 2nd Edition Tutorial 7

  15. FORMATTING NUMBERS • XPath function format-number • Syntax: format-number (value, format) • Example: format-number (56823.847, “#,##0.00”) displays 56,823.85 • Another example: format-number (56823.847, “#.##0,00”) displays 56.823,85 New Perspectives on XML, 2nd Edition Tutorial 7

  16. NUMBER FORMAT SYMBOLS New Perspectives on XML, 2nd Edition Tutorial 7

  17. <XSL:DECIMAL-FORMAT> • Format: <xsl:decimal-format attributes /> • Example: <xsl:decimal-format name=“Europe” decimal-separator=“,” grouping separator=“.” /> New Perspectives on XML, 2nd Edition Tutorial 7

  18. <XSL:DECIMAL-FORMAT> ATTRIUTES New Perspectives on XML, 2nd Edition Tutorial 7

  19. WORKING WITH TEXT NODES AND WHITE SPACE • White space: • Space (press space bar), &#x20; • Tab (pressing the tab key) &#x9; • new line (pressing Enter key) &#xA; • carriage return &#xD; • nonbreaking space &#160; • Adjacent <xsl:value-of> elements will have no white space between them • <xsl:text> can be used to create white space: • Syntax: <xsl:text>&#160</xsl:text> New Perspectives on XML, 2nd Edition Tutorial 7

  20. CONTROLLING WHITESPACE • Stripping space: • Remove text nodes that contain only white space from the result document • Syntax: <xsl:strip-space elements=“list”> • where list is a white-space separated list of elements in the source document that contain white space characters • Use * match all nodes New Perspectives on XML, 2nd Edition Tutorial 7

  21. CONTROLLING WHITESPACE • Preserving space: • Make sure that text nodes that contain only white space are not deleted • Syntax: <xsl:preserve-space elements=“list”> • Use * as pattern to match all nodes • Normalize space: • Remove leading and trailing spaces • X-pathSyntax: normalize-space(text) • Example: normalize-space (“ goodbye ”) returns the text string “goodbye” New Perspectives on XML, 2nd Edition Tutorial 7

  22. USING VARIABLES • User-defined name that stores a particular value or object, such as: • Types: • number • text string • node set • boolean value (either true or false) • result tree fragment New Perspectives on XML, 2nd Edition Tutorial 7

  23. VARIABLE SCOPE • Global: • 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 <xsl:stylesheet> element • Must have a unique variable name • Local: • Referenced only within template • Can share name with other local or global variable New Perspectives on XML, 2nd Edition Tutorial 7

  24. USING VARIABLES • Declaring variables • Syntax: <xsl:variable name=“name” select=“value” /> • Example: <xsl:variable name=“Months” select=“12” /> • Names are case-sensitive • Value only set once upon declaration • Enclose text strings in single-quotes • Example <xsl:variable name=“company” select=“‘Wizard Works’” /> • Referencing a variable: The name of the company is <xsl:value-of select=“$company” /> Not like variables of other languages Note use of $ New Perspectives on XML, 2nd Edition Tutorial 7

  25. COPYING • <xsl:copy> • Syntax: <xsl:copy use-attribute-sets=“list” /> • Shallow copy: only node itself is copied • <xsl:copy-of> • Syntax: <xsl:copy-of select=“expression”/> • Deep copy: node and descendants are copied • Example: <tr> <td><xsl:value-of select=“@date” /> </td> <tr> New Perspectives on XML, 2nd Edition Tutorial 7

  26. USING PARAMETERS • Similar to variables, but: • Value can be changed after it is declared • Can be set outside of scope • Syntax: <xsl:param name=“name” select=“value”/> • Example: <xsl:param name=”Filter” select=”'C103'” /> • To reference: $param-name New Perspectives on XML, 2nd Edition Tutorial 7

  27. SETTING PARAMETER VALUES EXTERNALLY • Depends on XSLT processor • Some work by appending parameter value to url • Web browsers to not allow users to set parameters values directly • Use a JavaScript program from within the browser (see Tutorial 10) New Perspectives on XML, 2nd Edition Tutorial 7

  28. TEMPLATE PARAMETERS • Local in scope • Created inside <xsl:template> element • To pass parameter to template • place <xsl:with-param> element in <xsl:apply-templates> element • Syntax: <xsl:with-param name=“name” select=“value”/> • No error if calling param name does not match template param name New Perspectives on XML, 2nd Edition Tutorial 7

  29. TEMPLATE PARAMETERS • Example <xsl:apply-templates select=“customers/customer”> <xsl:with-param names=“custID” select=“C101” /> </xsl:apply-templates> … <xsl:template match=“customer”> <xsl:parm name=“custID”/> styles </xsl:tmplate> New Perspectives on XML, 2nd Edition Tutorial 7

  30. INTRODUCING FUNCTIONAL PROGRAMMING • Functional programming language: • Relies on the evaluation of functions and expressions, not sequential execution of commands • Different from most other languages New Perspectives on XML, 2nd Edition Tutorial 7

  31. FUNCTIONAL PROGRAMMING PRINCIPLES • Main program consists entirely of functions with well-defined inputs • Results of program are defined in terms of function outputs • No assignment statements; when a variable is declared, its value cannot be changed • Order of the execution is irrelevant New Perspectives on XML, 2nd Edition Tutorial 7

  32. FUNCTIONAL PROGRAMMING • Easier to maintain and less susceptible to error • No order of execution • Each time a function is called, it does the same thing, regardless of how many times it has already been called, or the condition of other variables in the program • Important to think about the desired end result, rather than the sequential steps needed to achieve that effect New Perspectives on XML, 2nd Edition Tutorial 7

  33. RECURSION • In functional programming, recursion takes the place of looping structures • Function calls itself New Perspectives on XML, 2nd Edition Tutorial 7

  34. USING NAMED TEMPLATES • Template not associated with node set • Collection of functions and commands that are accessed from other templates in the style sheet • Syntax: <xsl:template name="name"> styles, variables and parameters </xsl:template> New Perspectives on XML, 2nd Edition Tutorial 7

  35. USING NAMED TEMPLATES • Example <xsl:template name=“totalCost”/> <xsl:param name=“list” /> <xsl: parm name=“total” select = “0” /> <!– Calculate the total item cost /> </sxl:template> New Perspectives on XML, 2nd Edition Tutorial 7

  36. CALLING NAMED TEMPLATES • Syntax: <xsl:call-template name=“name”> <xsl:with-param /> <xsl:with-param /> ... </xsl:call-template> New Perspectives on XML, 2nd Edition Tutorial 7

  37. WRITING A RECURSIVE TEMPLATE • Templates that call themselves, usually passing along a new parameter value with each call • Needs to have a stopping condition • Expressed in an if statement or a choose statement • If missing, will call itself without end New Perspectives on XML, 2nd Edition Tutorial 7

  38. WRITING A RECURSIVE TEMPLATE • Syntax with <xsl:if>: New Perspectives on XML, 2nd Edition Tutorial 7

  39. WRITING A RECURSIVE TEMPLATE • Syntax with <xsl:choose> New Perspectives on XML, 2nd Edition Tutorial 7

  40. WORKING WITH MULTIPLE STYLE SHEETS • Use <xsl:include> or <xsl:import> • Not supported by all browsers • Use to create a library of XSLT code • <xsl:include> • Syntax: <xsl:include href=“URL” /> • Same as inserting the components of included sheet directly into including file • Does not perform a direct text copy • Does not copy opening and closing <xsl:stylesheet> tags • Copies the elements and templates within the style sheet New Perspectives on XML, 2nd Edition Tutorial 7

  41. WORKING WITH MULTIPLE STYLE SHEETS • <xsl:import> • Syntax: <xsl:import href=”URL” /> • Must be at the top level of the style sheet; must be first child of <xsl:stylesheet> • If name conflicts occur, importing sheet takes precedence • If you import several style sheets, the last one imported has the highest precedence among the imported sheets in the event of a name conflict. New Perspectives on XML, 2nd Edition Tutorial 7

  42. WORKING WITH EXTENSION FUNCTIONS • Provide extended functionality specific to XSLT processor • Caution: use extensions only when you are sure that a given document is always acessed using the same processor. • Extension functions - extend the list of functions available to XPath and XSLT expressions • Extension elements - extend the list of elements that can be used in an XSLT style sheet • Extension attributes - extend the list of attributes associated with XSLT elements • Extension attribute values - extend the data types associated with XSLT attributes New Perspectives on XML, 2nd Edition Tutorial 7

  43. WORKING WITH EXTENSION FUNCTIONS • Check processor documentation for support • EXSLT: • Proposed common set of extensions • Not fully supported by all processors • Some functions supported by: • 4XSLT • saxon • jd.xslt • libxslt • Xalan-J Because extension functions are not available on all XSLT processors, just be aware of them. They will not be on the final exam New Perspectives on XML, 2nd Edition Tutorial 7

  44. USING EXTENSIONS • Modify <xsl:stylesheet> to include: <xsl:stylesheet version=”1.0” xmlns:xsl=”http://www.w3.org/1999/XSL/Transform” xmlns:math=”http://www.exslt.org/math” extension-element-prefixes=”math”> • Syntax: prefix:function() • Test function availability: function-available(“extension”) New Perspectives on XML, 2nd Edition Tutorial 7

  45. EXSLT MATH FUNCTIONS New Perspectives on XML, 2nd Edition Tutorial 7

  46. WRITING EXTENSION FUNCTIONS (MSXML) Processor used by IE • Add: <msxsl:script language=“language” implements-prefix=“refix”> script commands </msxsl:script> where language is the language of the script and prefix is the namespace prefix you want to assign to the extension functions script commands are the commands needed to create the extension function New Perspectives on XML, 2nd Edition Tutorial 7

  47. Example: random() <xsl:stylesheet version=“1.0” xmlns:xsl=“http://www.w3.org/1999/XSL/Transform” xmlns:jsext:=“http://javacrript-extensions” xmlns:msxsl=“urn:schema-microsoft-com:xslt” extension-element-prefixes=“jsextmasxsl”> <maxsl:script implements-prefix=“jsext” language = “javscript”> function random() { returns Math.random(); } </maxsl:script> <xsl:value-of select=“jsext:random()” /> Works only with MSXML New Perspectives on XML, 2nd Edition Tutorial 7

  48. SUMMARY • <xsl:number> and position() are used to number elements • XPath provides mathematical and string operators • Standard mathematical operators (+, -, etc.) can be used in XSLT • Number formatting uses format-number() function New Perspectives on XML, 2nd Edition Tutorial 7

  49. SUMMARY • White space characters are controlled with various XSLT elements and XPath functions • Variables and parameters are used to supply user-defined values • XSLT is a functional programming language • Recursive templates provide looping logic in XSLT • EXSLT provides a set of extension functions, elements, attributes and attribute values New Perspectives on XML, 2nd Edition Tutorial 7

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