Qualified Names, Prefixes, and Local Parts
Since URIs frequently contain characters such as /
, %
,
and ~
that are not legal in XML
names, short prefixes such as rdf
and
xsl
stand in for them in element
and attribute names. Each prefix is associated with a URI. Names whose prefixes
are associated with the same URI are in the same namespace. Names
whose prefixes are associated with different URIs are in different
namespaces. Prefixed elements and attributes in namespaces have
names that contain exactly one colon. They look like this:
rdf:description xlink:type xsl:template
Everything before the colon is called the prefix. Everything after the colon is called the local part. The complete name, including the colon, is called the qualified name , QName, or raw name. The prefix identifies the namespace to which the element or attribute belongs. The local part identifies the particular element or attribute within the namespace.
In a document that contains both SVG and MathML set
elements, one could be an svg:set
element, and the other could be a mathml:set
element. Then there’d be no
confusion between them. In an XSLT stylesheet that transforms
documents into XSL formatting objects, the XSLT processor would
recognize elements with the prefix xsl
as XSLT instructions and elements with
the prefix fo
as literal result
elements.
Prefixes may be composed from any legal XML name character
except the colon. The three-letter prefix xml
used for standard XML attributes such
as xml:space
, xml:lang ...
Get XML in a Nutshell, 3rd Edition now with the O’Reilly learning platform.
O’Reilly members experience books, live events, courses curated by job role, and more from O’Reilly and nearly 200 top publishers.