xml Namespaces Scope of namespace bindings

Example

A namespace binding (special xmlns or xmlns:... attribute) is in scope for all the descendants of the enclosing element, including this element.

<?xml version="1.0"?>
<root>
  <my:element xmlns:my="http://www.example.com/ns1">
    <!-- here, the prefix my is bound to http://www.example.com/ns1 -->
  </my:element>
  <my:element xmlns:my="http://www.example.com/ns2">
    <!-- here, the prefix my is bound to http://www.example.com/ns2 -->
  </my:element>
</root>

The binding can be overriden in a nested element (this affects readability though):

<?xml version="1.0"?>
<my:element xmlns:my="http://www.example.com/ns1">
  <!-- here, the prefix my is bound to http://www.example.com/ns1 -->
  <my:first-child-element/>

  <my:child-element xmlns:my="http://www.example.com/ns2">
    <!-- here, the prefix my is bound to http://www.example.com/ns2,
         including for the element my:child-element -->
  </my:child-element>

  <!-- here, the prefix my is bound to http://www.example.com/ns1 -->
  <my:last-child-element/>

</my:element>

It is very common to declare all namespace bindings in the root element, which improves readability.

<?xml version="1.0"?>
<root
  xmlns="http://www.example.com/default-namespace"
  xmlns:ns1="http://www.example.com/ns1"
  xmlns:ns2="http://www.example.com/ns2">
  
  <ns1:element>
    <ns2:other-element/>
  </ns1:element>

</root>