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Mastering XPath: Examples & Practice with Llandwp Members XML

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Learn XPath data model with structured location paths, axes, node tests, predicates, and examples in BaseX using Llandwp Members XML. Practice filtering nodes and attributes efficiently.

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Mastering XPath: Examples & Practice with Llandwp Members XML

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  1. Xpath Examples Edel Sherratt

  2. Llandwp Sports Club Members <?xml version="1.0"?> <?xml-stylesheet type="text/xml" href="members.xsl"?> <members> … <member> …</member> <member> …</member> … </members>

  3. XPath Data Model

  4. XPath examples to try in BaseX with LlandwpMembers.xml • /child::members • /descendant::member • /descendant::member[@number="17"] • /descendant::sport[string()="soccer"] • /descendant::sport[string()="soccer"]/ancestor::member • /descendant::com_role/ancestor::member • /descendant::sport[string()="squash"]/ancestor::member/name

  5. Structure of an XPath location path • /step/step/step … • step/step … • Each step in the location path has three parts • axis • nodetest • predicates • axis::nodetest[predicate][predicate]…

  6. What each step means • Starting from a context (you are here) • Specify an axis: parent, child, ancestor, descendant, attribute … • Filter the axis to get the kind of nodes you want (e.g., name an element) • Then filter again using expressions to get the precise nodes you want • do the same until all the steps are complete

  7. More examples to try in BaseX with LlandwpMembers.xml • /descendant::renewal_due • /descendant::renewal_due/ancestor::member • /descendant::sport[string()="soccer"]/ancestor::member • /descendant::sport[string()="soccer"]/ancestor::member/child::name • /descendant::team[string()="Soccer A"]/ancestor::member/child::name • /descendant::member/attribute::number

  8. More about node tests • A name returns nodes with that name • node() selects all nodes • processing-instruction() returns processing instructions • text() selects character data nodes • comment() selects comment nodes

  9. Examples to try with LlandwpMembers.xml • /child::processing-instruction() • /child::members • /child::node() • /descendant::member • /descendant::member/descendant::text() • /descendant::sport • /descendant::sport/child::text()

  10. Some shortcuts • child is the default axis, so /members is equivalent to /child::members • // is shorthand for /descendant-or-self::node(), so //name is equivalent to /descendant-or-self::node()/name • . is shorthand for self::node() • .. is shorthand for parent::node()

  11. More queries to try • //sport • //sport/.. • //sport/../.. • //sport/../../name

  12. And yet more … • /processing-instruction() • /members • /node() • //member//text() • //name • //name/text()

  13. And more • //renewal_due • //renewal_due/ancestor::member • //sport[string()="soccer"]/ancestor::member • //sport[string()="soccer"]/ancestor::member/name • //team[string()="Soccer A"]/ancestor::member/name

  14. Wildcards in node tests • node() matches any kind of node • * matches any element • @* matches any attribute

  15. Final set of examples • //team[string()="Soccer A"]/ancestor::member/@number • //team[string()="Soccer A"]/ancestor::member/@* • /* • /node() • //@*

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