j'c'westlakestaffs'ac'uk

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Expression Builder

• Useful tool for testing out XPath
• Once unzipped you can fire up a screen as on the
  next slide
• XML instance will be the XML document you wish
  to use i.e. a .xml file in this case
  contacts.xml
• In the node-set expression box you can type the
  XPath expression you wish to use

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Selecting Nodes

• XPath uses path expressions to select nodes in an
  XML document. The node is selected by following a
  path or steps. The most useful path expressions
  are listed below
• 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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XPath expresssions examples

• contactlist - Selects the root element
• /contactlist does the same thing
• /contactlist/contact - Selects all contact
  elements that are children of contactlist
• //contact - Selects all contact elements no
  matter where they are in the document
• contactlist//contact - Selects all contact
  elements that are descendant of the contactlist
  element, no matter where they are under the
  contactlist element
• //_at_owner - Selects all attributes that are named
  owner

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examples

• //contactlist/_at_ Selects all title elements
  which have any attribute
• // selects all elements in the document
• /contactlist/contact1 should work! And find
  the 1st instance of the element
• Doesnt work at present in the expression builder

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For more about XPath

• Visit w3schools.com