xmlnsprefix

xmlnsprefix is a label sometimes used to refer to the namespace prefix in XML documents. In XML, a namespace prefix is a shorthand label that stands for a namespace URI, allowing elements and attributes from different vocabularies to be used without name collisions. A namespace is declared with xmlns:prefix="URI" within an element, and the mapping remains in effect for the element's scope and its descendants.

Note that the XML specification reserves two prefixes: the xml prefix bound to http://www.w3.org/XML/1998/namespace and the xmlns prefix used for namespace declarations. The xml prefix is read-only and must not be rebound; the xmlns prefix is only used in declarations and cannot be used as a normal element or attribute prefix.

Most XML processing models (DOM, SAX, XPath, XSLT) expose the mapping between a prefix and a namespace URI. In canonical form, names are represented by their namespace URI and local name; the prefix is not necessary for identity, though it is commonly used in serialized XML. Some APIs store or expose a separate xmlnsprefix value to preserve the original prefix or to facilitate round-tripping, but such storage is implementation-specific.

Best practices include choosing stable, meaningful prefixes, avoiding reliance on a default namespace for critical elements unless designed, and ensuring that prefixes are redeclarable in inner scopes without conflicting with outer declarations.

See also: XML Namespaces, Namespace Prefix, Namespace URI, XML Infoset, XPath, XSLT.