XML NAMESPACES

Definition: An XML namespace is identified by a URI reference [RFC3986]; element and attribute names may be placed in an XML namespace using the mechanisms described in this specification.
Definition: An expanded name is a pair consisting of a namespace name and a local name. Definition: For a name N in a namespace identified by a URI I, the namespace name is I. For a name N that is not in a namespace, the namespace name has no value. Definition: In either case the local name is N. It is this combination of the universally managed IRI namespace with the vocabulary's local names that is effective in avoiding name clashes.
URI references can contain characters not allowed in names, and are often inconveniently long, so expanded names are not used directly to name elements and attributes in XML documents. Instead qualified names are used. [Definition: A qualified name is a name subject to namespace interpretation .In documents conforming to this specification, element and attribute names appear as qualified names. Syntactically, they are either prefixed names or unprefixed names. An attribute-based declaration syntax is provided to bind prefixes to namespace names and to bind a default namespace that applies to unprefixed element names; these declarations are scoped by the elements on which they appear so that different bindings may apply in different parts of a document. Processors conforming to this specification MUST recognize and act on these declarations and prefixes.