Default namespace for encoded XML

In an XML instance document that uses namespaces, there is an option to define a default namespace. In this way, all unqualified XML elements in the XML document are processed as being qualified by this default namespace.

For example:

Without the default namespace declared:

<?xml version="1.0"?>
<apo:purchaseOrder xmlns:apo="http://www.example.com/PO1"
                                     orderDate="1999-10-20">
                <apo:shipTo country="US">
                        <apo:name>Alice Smith</apo:name>
                        <apo:street>123 Maple Street</apo:street>
                        <!-- etc. -->
                </apo:shipTo>
                <apo:billTo country="US">
                        <apo:name>Robert Smith</apo:name>
                        <apo:street>8 Oak Avenue</apo:street>
                        <!-- etc. -->
                </apo:billTo><apo:comment>Hurry, my lawn is going wild<!/apo:comment>
                <!-- etc. -->
</apo:purchaseOrder>

With the default namespace declared:

<?xml version="1.0"?>
<purchaseOrder xmlns="http://www.example.com/PO1"
                             orderDate="1999-10-20">
                <shipTo country="US">
                        <name>Alice Smith</name>
                        <street>123 Maple Street</street>
                        <!-- etc. -->
                </shipTo>
                <billTo country="US">
                        <name>Robert Smith</name>
                        <street>8 Oak Avenue</street>
                        <!-- etc. -->
                </billTo>
                <comment>Hurry, my lawn is going wild<!/comment>
                <!-- etc. -->
</purchaseOrder>