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XML Path Language (XPath)

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XML Path Language (XPath). Outline 11.1 Introduction 11.2 Nodes 11.3 Location Paths 11.3.1 Axes 11.3.2 Node Tests 11.3.3 Location Paths Using Axes and Node Tests 11.4 Node-set Operators and Functions. 11.1 Introduction. XML Path Language (XPath)

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XML Path Language (XPath)

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  1. XML Path Language (XPath) Outline11.1 Introduction11.2 Nodes11.3 Location Paths 11.3.1 Axes 11.3.2 Node Tests 11.3.3 Location Paths Using Axes and Node Tests11.4 Node-set Operators and Functions

  2. 11.1 Introduction • XML Path Language (XPath) • Syntax for locating information in XML document • e.g., attribute values • String-based language of expressions • Not structural language like XML • Used by other XML technologies • XSLT • XPointer

  3. 11.2 Nodes • XML document • Tree structure with nodes • Each node represents part of XML document • Seven types • Root • Element • Attribute • Text • Comment • Processing instruction • Namespace • Attributes and namespaces are not children of their parent node • They describe their parent node

  4. 1 <?xml version = "1.0"?> Root node 2 Comment nodes 3 <!-- Fig. 11.1 : simple.xml --> 4 <!-- Simple XML document --> Element nodes Attribute nodes 5 6 <book title = “XML at Santa Ana College"edition = "3"> 7 Text nodes 8 <sample> 9 <![CDATA[ 10 11 // C++ comment 12 if ( this->getX() < 5 && value[ 0 ] != 3 ) 13 cerr << this->displayError(); 14 ]]> 15 </sample> 16 17 XML at Santa Ana College by CS Staff 18 </book> Fig. 11.1 Simple XML document.Root node Comment nodes Element nodesAttribute nodesText nodes

  5. Fig. 11.2 XPath tree for Fig. 11.1. Root CommentFig. 11.1 : simple.xml CommentSimple XML document Elementbook AttributeTitleXML at Santa Ana College Attributeedition 3 Elementsample Text// C++ comment if (this -> getX() < 5 && value[ 0 ] != 3 ) cerr << this->displayError(); TextXML at Santa Ana College by CS Staff

  6. 1 <?xml version = "1.0"?> Root node 2 Comment nodes 3 <!-- Fig. 11.3 : simple2.xml --> 4 <!-- Processing instructions and namespacess --> 5 Namespace nodes Processing instruction node 6 <html xmlns = "http://www.w3.org/TR/REC-html40"> Element nodes 7 Text nodes 8 <head> 9 <title>Processing Instruction and Namespace Nodes</title> Attribute nodes 10 </head> 11 12 <?processor example = "fig11_03.xml"?> 13 14 <body> 15 16 <sac:book cssac:edition = "1" 17 xmlns:sac = "http://sacbusiness.org/xmlns"> 18 <sac:title>XML</sac:title> 19 </sac:book> 20 21 </body> 22 23 </html> Fig. 11.3 XML document with processing-instruction and namespace nodes.Root nodeComment nodesNamespace nodesProcessing instruction nodeElement nodesText nodesAttribute nodes

  7. Fig. 11.4 Tree diagram of an XML documentwith a processing-instruction node Root CommentFig. 11.3 : simple2.xml CommentProcessing instructions and namespaces Elementhtml Namespacehttp://www.w3.org/TR/REC-html40 Elementhead Elementtitle TextProcessing instructions and Namespace Nodes Continued on next slide...

  8. Fig. 11.4 Tree diagram of an XML document with a processing-instruction node. (Part 2) Continued from previous slide Processing Instructionprocessorexample = "fig11_03.xml" Elementbody Elementbook Attributeedition1 Namespacehttp://sacbusiness.org/xmlns Elementtitle TextXML

  9. Fig. 11.5 XPath node types

  10. Fig. 11.5 XPath node types. (Part 2)

  11. 11.3 Location Paths • Location path • Expression specifying how to navigate XPath tree • Composed of location steps • Each location step composed of • Axis • Node test • Predicate

  12. 11.3.1 Axes • XPath searches are made relative to context node • Axis • Indicates which nodes are included in search • Relative to context node • Dictates node ordering in set • Forward axes select nodes that follow context node • Reverse axes select nodes that precede context node

  13. Fig. 11.6 XPath axes.

  14. 11.3.2 Node Tests • Node tests • Refine set of nodes selected by axis • Rely upon axis’ principle node type • Corresponds to type of node axis can select

  15. Fig. 11.7 Some XPath node tests.

  16. 11.3.3 Location Paths Using Axes and Node Tests • Location step • Axis and node test separated by double colon (::) • Optional predicate enclosed in square brackets ([]) • Some examples: • Select all element-node children of context node child::* • Select all text-node children of context nodechild::text() • Select all text-node grandchildren of context node child::*/child::text()

  17. Fig. 11.8 Some location-path abbreviations.

  18. 1 <?xml version = "1.0"?> 2 3 <!-- Fig. 11.9 : books.xml --> 4 <!-- XML book list --> 5 6 <books> 7 8 <book> 9 <title>Java</title> 10 <translation edition = "1">Spanish</translation> 11 <translation edition = "1">Danish</translation> 12 <translation edition = "1">Japanese</translation> 13 <translation edition = "2">French</translation> 14 <translation edition = "2">Japanese</translation> 15 </book> 16 17 <book> 18 <title>C++</title> 19 <translation edition = "1">Swedish</translation> 20 <translation edition = "2">French</translation> 21 <translation edition = "2">Spanish</translation> 22 <translation edition = "3">Finnish</translation> 23 <translation edition = "3">Japanese</translation> 24 </book> 25 26 </books> Fig. 11.9 XML document that marks up book translations.

  19. Fig. 11.10 XPath tree for books.xml Othernodes… Elementbook Elementtitle TextJava Elementtranslation Attributeedition 1 TextSpanish Elementtranslation Attributeedition 1 Text Danish Continued on next slide…

  20. Fig. 11.10 XPath tree for books.xml Continued from previous slide… Elementtranslation Attributeedition 1 TextJapanese Elementtranslation Attributeedition 2 TextFrench Elementtranslation Attributeedition 2 TextJapanese Othernodes…

  21. 11.3.3 Location Paths Using Axes and Node Tests (cont.) • Which books have Japanese translations? • Use root node of XPath tree as context node • Use predicate • Boolean expression for filtering nodes from search • Compare string value of current node to string ‘Japanese’ /books/book/translation[. = ‘Japanese’]/../title

  22. 11.4 Node-set Operators and Functions • Node-set operators • Manipulate node sets to form others • Node-set functions • Perform actions on node-sets returned by location paths

  23. Fig. 11.11 Node-set operators.

  24. Fig. 11.12 Some node-set functions.

  25. 11.4 Node-set Operators and Functions (cont.) • Location-path expressions • Combine node-set operators and functions • Select all head and body children element nodes head | body • Select last bold element node in head element node head/title[ last() ] • Select third book element book[ position() = 3 ] • Or alternatively book[ 3 ] • Return total number of element-node children count( * ) • Select all book element nodes in document //book

  26. 1 <?xml version = "1.0"?> 2 3 <!-- Fig. 11.13 : stocks.xml --> 4 <!-- Stock list --> 5 6 <stocks> 7 8 <stock symbol = "INTC"> 9 <name>Intel Corporation</name> 10 </stock> 11 12 <stock symbol = "CSCO"> 13 <name>Cisco Systems, Inc.</name> 14 </stock> 15 16 <stock symbol = "DELL"> 17 <name>Dell Computer Corporation</name> 18 </stock> 19 20 <stock symbol = "MSFT"> 21 <name>Microsoft Corporation</name> 22 </stock> 23 24 <stock symbol = "SUNW"> 25 <name>Sun Microsystems, Inc.</name> 26 </stock> 27 28 <stock symbol ="CMGI"> 29 <name>CMGI, Inc.</name> 30 </stock> 31 32 </stocks> Fig. 11.13 List of companies with stock symbols.

  27. 1 <?xml version = "1.0"?> 2 3 <!-- Fig. 11.14 : stocks.xsl --> 4 <!-- string function usage --> 5 6 <xsl:stylesheet version = "1.0" 7 xmlns:xsl = "http://www.w3.org/1999/XSL/Transform"> XPath string functions 8 9 <xsl:template match = "/stocks"> 10 <html> 11 <body> 12 <ul> 13 14 <xsl:for-each select = "stock"> 15 16 <xsl:if test = 17 "starts-with(@symbol, 'C')"> 18 19 <li> 20 <xsl:value-of select = 21 "concat(@symbol,' - ', name)"/> 22 </li> 23 </xsl:if> 24 25 </xsl:for-each> 26 </ul> 27 </body> 28 </html> 29 </xsl:template> 30 </xsl:stylesheet> Fig. 11.14 Demonstrating some String functions.XPath string functions

  28. Output for Fig. 11.14

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