![XML: Find 3rd Vehicle:
<vehicles> /vehicles/vehicle[2]
<vehicle model="camaro">
<year>1967</year> (1-based numbering)
<engine>327 v8</engine>
</vehicle> Find vehicles that are from ‘72:
<vehicle model="challenger"> /vehicles/vehicle/[year=‘1972’]
<year>1972</year>
<engine>383 v8</engine> (return a node set)
</vehicle>
<vehicle model="baja bug">
<year>multiple</year>
<engine>1200
opposing4</engine>
</vehicle>
</vehicles>](https://image.slidesharecdn.com/xpath-111106175955-phpapp01/85/XPath-13-320.jpg)
XPath
- 1. CIS-189
- 2. XPath provides a logical model for working with XML document Nodes are used to represent serialized XML (in memory) ◦ Not all parts of XML document are represented (XML declaration, DOCTYPE) XPath is used in combination with other tools (such as XSLT)
- 3. Legal XPath code is called an expression ◦ An XPath expression that return a node set is a location path Expressions can be absolute and relative ◦ Absolute path includes a full definition of how to find node ◦ Relative path is based on current context (location)
- 4. Root node represents document ◦ Can have only one child node (document element) Element node represents elements ◦ QName (qualified name) includes namespace prefix and element name Attribute node represent attributes ◦ Have name and value ◦ Are not represented as child nodes Text node represents text value of an element ◦ Does not have a name Namespace node gives access to the namespace URI and prefix Comment node Processing Instruction Node
- 5. Boolean ◦ Written as true() and false() String Number – floating point values Node-set – unordered set ◦ Follows document order
- 6. Element node references can be spelled out or abbreviated /child::movies/child::movie/child::price OR /movies/movie/price ◦ child::nodename can also be written nodename Attribute node references attribute::attributename OR @attributename
- 7. self following child following-sibling attribute namespace ancestor parent ancestor-or-self preceding descendant preceding-sibling descendent-or-self
- 8. Default axis Selects nodes that are immediate nodes of context (current) node Can use * to refer to all child nodes
- 9. <movie> If context is movie <title>Up</title> Location path <price>4.99</price child::copy (or > copy) returns node <copy>1</copy> set with both copy <copy>2</copy> elements Location path </movie> child::* (or *) returns node set with title, price, 2 copy nodes
- 10. Can use node() to return all child nodes including comments, processing instructions, and text nodes Can return just text nodes using text() ◦ Text nodes are unnamed
- 11. Used to select attributes belonging to a particular element node To return all attributes ◦ attribute::* ◦ @* To return particular attribute ◦ attribute::attributename ◦ @attributename
- 12. Used to filter node sets ◦ Predicate similar to query criteria Can use specific values or location references
- 13. XML: Find 3rd Vehicle: <vehicles> /vehicles/vehicle[2] <vehicle model="camaro"> <year>1967</year> (1-based numbering) <engine>327 v8</engine> </vehicle> Find vehicles that are from ‘72: <vehicle model="challenger"> /vehicles/vehicle/[year=‘1972’] <year>1972</year> <engine>383 v8</engine> (return a node set) </vehicle> <vehicle model="baja bug"> <year>multiple</year> <engine>1200 opposing4</engine> </vehicle> </vehicles>