xmlns
xmlns is a feature of the XML Namespaces specification that enables disambiguation of element and attribute names when combining XML vocabularies. It works by declaring a mapping between a short prefix and a namespace URI, using either xmlns:prefix="URI" or xmlns="URI" for a default namespace. The declared mappings apply to the element on which the declaration appears and to all of its descendants, unless they are overridden by later declarations.
For example, a document might start with: <library xmlns="http://example.org/books" xmlns:dc="http://purl.org/dc/elements/1.1/">
<dc:title>Catalog Title</dc:title>
</library>. In this snippet, unprefixed elements like title belong to the default namespace http://example.org/books, while the
Important notes: default namespaces affect element names but not attributes; to place an attribute in a namespace
Namespaces help prevent name collisions and enable mixing of vocabularies in XML-based standards such as XHTML,
Common pitfalls include assuming the default namespace applies to attributes, or assuming that the actual URL