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Node Functions

Node functions report a node's identity and content: name(), local-name(), namespace-uri() and node-name() (Namespaces and xml: Attributes), root(), base-uri() and document-uri(), string() (all descendant text joined) and data() (the typed value). XPath 3.0 added path(), which writes an absolute path to any node, has-children(), and innermost() and outermost(), which drop nodes nested inside other nodes of the same sequence:

Node identity, location and content functions on the catalog
xp 'local-name((//price)[1])' 'path(//book[2]/title)' \
   'tokenize(document-uri(/), "/")[last()]' 'string(//book[1]/supply)' \
   'normalize-space(//book[1]/supply)' \
   'innermost(//book[1]/supply/descendant-or-self::*) ! name()' 'generate-id(//book[1])'
Output
local-name((//price)[1])               => "price"
path(//book[2]/title)                  => "/Q{}catalog[1]/Q{}book[2]/Q{}title[1]"
tokenize(document-uri(/), "/")[last()] => "booknest-catalog.xml"
string(//book[1]/supply)               => "       in-stock       14.99     "
normalize-space(//book[1]/supply)      => "in-stock 14.99"
innermost(//book[1]/supply/descendant-or-self::*) ! name() => "availability" "price"
generate-id(//book[1])                 => "d0e13"

path() writes each step as Q{namespace}name[position] (empty braces here, as the catalog has no namespace), which makes it ideal for error reports that must locate a bad value in a large feed. string() on an element concatenates its text nodes, indentation included (the xp wrapper shows the embedded newlines as spaces), so clean it with normalize-space(). generate-id() returns a key that is stable only within one run, so never store it as an identifier.

Node Functions

Node functions return information about nodes in the XDM tree — their names, namespace, base URI, string value, structural path, and other properties. The examples below evaluate against this sample document, an extended version of the <menu> example used in Path Expressions, here with an added xml:lang attribute, an ns namespace prefix, and an xml:id on the first <dish>:
<?xml version="1.0"?>
<menu restaurant="Golden Outlet" xmlns:ns="http://example.com" xml:lang="en">
  <dish xml:id="1">Satay <i>Cooked</i></dish>
  <drink id="2">Cola</drink>
  <dish id="3">Curry Chicken</dish>
  <dish id="4" xmlns="http://example.com">Sweet and Sour Pork</dish>
</menu>

Each of the following returns the string dish:
name(menu/ns:dish)
menu/dish[1]/name()
node-name(menu/ns:dish)
local-name(menu/ns:dish)
id("1")/name()
element-with-id("1")/name()
idref("1")/name()

namespace-uri(menu/ns:dish) returns http://example.com.

Each of the following returns the base URI in effect for the evaluation context (e.g. /home/project-web/videlibri/cgi-bin/ for the online evaluator referenced in XPath):
base-uri(menu/ns:dish)
base-uri()
static-base-uri()

Each of the following returns an empty sequence, since the document was not loaded with doc() and therefore has no document URI:
document-uri()
document-uri(menu)

Each of the following returns the same string — the concatenated string value of every descendant text node of the document, including the whitespace between elements:    Satay Cooked   Cola   Curry Chicken   Sweet and Sour Pork
string()
string(menu)
data(menu)

Each of the following returns /, the structural path of the current node from the document root:
path()
path(.)

innermost(menu) returns the nodes in a node sequence that have no descendant node also present in that sequence — for the sample document: <i>Cooked</i>, <drink id="2">Cola</drink>, <dish id="3">Curry Chicken</dish>, and <dish id="4" xmlns="http://example.com">Sweet and Sour Pork</dish>.

outermost(menu/dish/i) returns the nodes in a node sequence that are not descendants of any other node in that sequence:
<?xml version="1.0"?>
<menu restaurant="Golden Outlet" xmlns:ns="http://example.com">
  <dish id="1">Satay <i>Cooked</i></dish>
  <drink id="2">Cola</drink>
  <dish id="3">Curry Chicken</dish>
  <dish id="4" xmlns="http://example.com">Sweet and Sour Pork</dish>
</menu>

nilled(menu) returns false, since the element has content and is not marked xsi:nil="true".

Each of the following returns true:
has-children()
has-children(menu)
lang("en")
lang("en",menu/dish)

generate-id() returns an implementation-dependent unique identifier string for the current node; the exact value is not standardized and differs between XPath processors.
ch03-node-functions-menu.xml, ch03-node-functions.xpath.txtXML
merged-01-01-ch03-node-functions-menu.xml
<?xml version="1.0"?>
<menu restaurant="Golden Outlet" xmlns:ns="http://example.com" xml:lang="en">
   <dish xml:id="1">Satay <i>Cooked</i></dish>
   <drink id="2">Cola</drink>
   <dish id="3">Curry Chicken</dish>
   <dish id="4" xmlns="http://example.com">Sweet and Sour Pork</dish>
</menu>
merged-01-02-ch03-node-functions.xpath.txt
namespace-uri(menu/ns:dish)
Output
http://example.com