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XPATH

XPATH. XPath. Primary goal = to permit to access some nodes from a given document XPath main construct : axis navigation An XPath path consists of one or more navigation steps, separated by / A navigation step is a triplet: axis + node-test + list of predicates Examples

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XPATH

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  1. XPATH

  2. XPath • Primary goal = to permit to access some nodes from a given document • XPath main construct : axis navigation • An XPath path consists of one or more navigation steps, separated by / • A navigation step is a triplet: axis + node-test + list of predicates • Examples • /descendant::node()/child::author • /descendant::node()/child::author[parent/attribute::booktitle = “XML”][2] • XPath also offers some shortcuts • no axis means child • // º /descendant-or-self::node()/

  3. context node aaa aaa ccc ccc aaa 2 3 1 bbb bbb 4 5 6 7 XPath- child axis navigation • author is shorthand for child::author. Examples: • aaa -- all the child nodes labeled aaa (1,3) • aaa/bbb -- all the bbb grandchildren of aaa children (4) • */bbb all the bbb grandchildren of any child (4,6) • . -- the context node • / -- the root node

  4. XPath- child axis navigation (cont) • /doc -- all the doc children of the root • ./aaa -- all the aaa children of the context node (equivalent to aaa) • text() -- all the text children of the context node • node() -- all the children of the context node (includes text and attribute nodes) • .. -- parent of the context node • .// -- the context node and all its descendants • // -- the root node and all its descendants • //text() -- all the text nodes in the document

  5. Predicates • [2] -- the second child node of the context node • chapter[5] -- the fifth chapter child of the context node • [last()] -- the last child node of the context node • chapter[title=“introduction”] -- the chapter children of the context node that have one or more title children whose string-value is “introduction” (the string-value is the concatenation of all the text on descendant text nodes) • person[.//firstname = “joe”] -- the person children of the context node that have in their descendants a firstname element with string-value “Joe” • From the XPath specification: NOTE: If $x is bound to a node set then $x = “foo” does not mean the same as not ($x != “foo”) ...

  6. Axis navigation • So far, nearly all our expressions have moved us down the by moving to child nodes. Exceptions were • . -- stay where you are • / go to the root • // all descendants of the root • .// all descendants of the context node • XPath has several axes: ancestor, ancestor-or-self, attribute, child, descendant, descendant-or-self, following, following-sibling, namespace, parent, preceding, preceding-sibling, self • Some of these (self, parent) describe single nodes, others describe sequences of nodes.

  7. XPath Navigation Axes(merci, Arnaud) ancestor preceding-sibling following-sibling self child attribute preceding following namespace descendant

  8. XPath abbreviated syntax (nothing) child:: @ attribute:: // /descendant-or-self::node() . self::node() .// descendant-or-self::node .. parent::node() / (document root)

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