AliasNamespaceDictionary getNamespaceAliases()
  Property NameDefaultNamespaceURI  
  Property Type string  
  Accessors Read Only  
  DescriptionA collection of name value pairs, containing a namespace URI and namespace Alias.  

These alias will be declared at the root level in the document.
The sample shows what you get if an alias “MyAlias”, and UIR "http://sample" are added to the collection.

<?xml version="1.0"?>
<MyAlias:Customer xmlns:MyAlias="http://sample"

Also See AliasNamespaceDictionary

public class AliasNamespaceDictionary {
    public String getNamespaceURI(String nsAlias);
    public java.util.Set getAliases();
    public java.util.Collection getNamespaces();
    public void add(String nsAlias, String namespaceUri);
    public boolean contains(String nsAlias);
    public void remove(String nsAlias);