XML namespace: Difference between revisions

Revision as of 21:19, 27 September 2006

Revision as of 02:52, 14 November 2006

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A namespace is declared using the reserved XML attribute <code>xmlns</code>, the value of which must be a [[Uniform Resource Identifier|URI]] (Uniform Resource Identifier) reference, e.g.:

<pre><nowiki>xmlns="http://www.w3.org/1999/xhtml"</nowiki></pre>

Note, however, that the URI is not actually read, as an online address; it is simply treated by an XML parser as a string. For example, [http://www.w3.org/1999/xhtml http://www.w3.org/1999/xhtml] itself does not contain any code, it simply describes the [[xhtml]] namespace to human readers. Using a URI (such as <nowiki>"http://www.w3.org/1999/xhtml"</nowiki>) to identify a namespace, rather than a simple string (such as "xhtml"), reduces the possibility of different namespaces using duplicate identifiers. Namespace identifiers need not follow the conventions of web addresses, though they often do.

The declaration can also include a short prefix with which elements and attributes can be identified, e.g.: <pre><nowiki>xmlns:xhtml="http://www.w3.org/1999/xhtml"</nowiki></pre>