Namespaces
Since XPointers may appear in places that are not XML
documents (HTML documents, database fields, magazine pages, etc.),
they require their own mechanism for binding namespace prefixes to namespace URIs. This is done by placing one or more xmlns
parts before the xpointer
part. The syntax is xmlns(
prefix
=
URI
)
. For example, this XPointer maps
the svg
prefix to the http://www.w3.org/2000/svg
namespace and
then searches out all rect
elements
in that namespace:
xmlns(svg=http://www.w3.org/2000/svg) xpointer(//svg:rect)
As with most other uses of namespaces, only the URI matters in
an XPointer, not the prefix. The previous XPointer finds all rect
elements in the namespace http://www.w3.org/2000/svg
, regardless of
what prefix they use or whether they’re in the default
namespace.
There is no way to define a default, unprefixed namespace for an
XPointer. However, prefixed names in an XPointer can refer to
unprefixed but namespace-qualified elements in the targeted document.
For example, this XPointer finds the third div
element in an XHTML document:
xmlns(html=http://www.w3.org/1999/xhtml) xpointer(//html:div[3])
It uses the prefix html
to
identify the XHTML namespace, even though XHTML documents never use
prefixes themselves.
More than one namespace prefix can be used simply by adding
extra xmlns
parts. For example,
this XPointer seeks out svg
elements in XHTML documents by declaring one prefix each for the SVG
and XHTML namespaces:
xmlns(svg=http://www.w3.org/2000/svg) xmlns(h=http://www.w3.org/1999/xhtml) ...
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