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
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>
